Expand all leading tabs in markdown files

Given how problematic leading tabs in markdown files can be,
we have expanded all leading tabs in markdown files by:

```sh
find * -type f -name '*.md' -print |
  while read -r file; do
    rm -f "$file.tmp" ;
    expand < "$file" > "$file.tmp" ;
    mv -f -v "$file.tmp" "$file" ;
  done
```

Given the previous changes to `bin/pandoc-wrapper.sh` and other recent
commits and recent pull requests, the were were **NO** changes to
any HTML files.  This is a **good thing** as the expression goes.

No there are no leading tabs in any markdown files.
A check to catch any re-introduction of leading tabs
into any markdown file is on the way.

BTW: We do not have anything against leading tabs in files,
even though we have had to deal with their impact on forming
HTML from markdown files (as well as the calc source code).
It is just that this is one of those cases where tabs conflict
(sometimes caused by people wanting to change the classic
8-space tab model) with a desired outcome.

Perform `make www` to perform the above and test under macOS.

2015/schweikhardt/README.md

@@ -58,9 +58,9 @@ Bell](http://members.tip.net.au/~dbell/) once described
 as having one of the largest "yummo quotients" in number theory:
 
 ```
-			 complexity of the solution
+                         complexity of the solution
     yummo quotient = -----------------------------------
-		     complexity of the problem statement
+                     complexity of the problem statement
 ```
 
 [Erdős](https://en.wikipedia.org/wiki/Paul_Erdős) privately told one of the IOCCC judges:
@@ -261,31 +261,31 @@ built. In biochemistry, each is assigned a TLI (see [Proteinogenic amino
 acid](https://en.wikipedia.org/wiki/Proteinogenic_amino_acid) for more info):
 
 ```
-    ala	Alanine
-    cys	Cysteine
-    asp	Aspartic acid
-    glu	Glutamic acid
-    phe	Phenylalanine
-    gly	Glycine
-    his	Histidine
-    ile	Isoleucine
-    lys	Lysine
-    leu	Leucine
-    met	Methionine
-    asn	Asparagine
-    pyl	Pyrrolysine
-    pro	Proline
-    gln	Glutamine
-    arg	Arginine
-    ser	Serine
-    thr	Threonine
-    sec	Selenocysteine
-    val	Valine
-    trp	Tryptophan
-	tyr	Tyrosine
-	asx	Asparagine or Aspartic acid
-	glx	Glutamic acid or Glutamine
-	xle	Leucine or Isoleucine
+    ala Alanine
+    cys Cysteine
+    asp Aspartic acid
+    glu Glutamic acid
+    phe Phenylalanine
+    gly Glycine
+    his Histidine
+    ile Isoleucine
+    lys Lysine
+    leu Leucine
+    met Methionine
+    asn Asparagine
+    pyl Pyrrolysine
+    pro Proline
+    gln Glutamine
+    arg Arginine
+    ser Serine
+    thr Threonine
+    sec Selenocysteine
+    val Valine
+    trp Tryptophan
+        tyr     Tyrosine
+        asx     Asparagine or Aspartic acid
+        glx     Glutamic acid or Glutamine
+        xle     Leucine or Isoleucine
     unk Unknown
 ```
 
@@ -294,10 +294,10 @@ the rule "[No original
 research](https://en.wikipedia.org/wiki/Wikipedia:No_original_research)"):
 
 ```
-    and	Androgynine
-    xor	Xenoricine
-    not	Notanamine
-    tla	Triletramine
+    and Androgynine
+    xor Xenoricine
+    not Notanamine
+    tla Triletramine
 ```
 
 Interestingly, the TLI are the perfect mnemonics for C language source.
@@ -336,23 +336,23 @@ Another identity operation. I've done it for you already. Use this
 
 ``` <!---sh-->
     $ cat .indent.pro
-	-bad   /* blank line after decls */
-	-bap   /* blank line after functions */
-	-br    /* braces on if line */
-	-i8    /* indent */
-	-l999  /* line length */
-	-npcs  /* no space after function call names */
-	-npsl  /* don't break procedure type */
-	-ut    /* use tabs */
-	-ce    /* cuddle else */
-	-nip   /* no parameter indentation */
-	-di1   /* declaration indent */
-	-Tand
-	-Tmet
-	-Tthr
-	-Tpro
-	-Tser
-	-Tala
+        -bad   /* blank line after decls */
+        -bap   /* blank line after functions */
+        -br    /* braces on if line */
+        -i8    /* indent */
+        -l999  /* line length */
+        -npcs  /* no space after function call names */
+        -npsl  /* don't break procedure type */
+        -ut    /* use tabs */
+        -ce    /* cuddle else */
+        -nip   /* no parameter indentation */
+        -di1   /* declaration indent */
+        -Tand
+        -Tmet
+        -Tthr
+        -Tpro
+        -Tser
+        -Tala
 ```
 
 It looks like a perfect program should have:
@@ -390,15 +390,15 @@ Pseudocode, with comments matching those in the C source:
        n = convert(argv[1])
        print n                       /* 2hx */
        while (n != 1) {              /* one */
-	  if (n is odd) {            /* odd */
-	     m = deep copy of n      /* cpy */
-	     n <<= 1                 /* shl */
-	     n += m                  /* add */
-	     increment n             /* inc */
-	  } else {                   /* eve */
-	     n >>= 1                 /* shr */
-	  }
-	  print n                    /* 2hx */
+          if (n is odd) {            /* odd */
+             m = deep copy of n      /* cpy */
+             n <<= 1                 /* shl */
+             n += m                  /* add */
+             increment n             /* inc */
+          } else {                   /* eve */
+             n >>= 1                 /* shr */
+          }
+          print n                    /* 2hx */
       }
     }
 ```
@@ -407,8 +407,8 @@ Pseudocode, with comments matching those in the C source:
 
 ``` <!---c-->
     typedef struct {
-	 size_t places;   /* number of places in base 2 to the power of (8*sizeof(type)) */
-	 type  *number;   /* dynamically allocated memory for number */
+         size_t places;   /* number of places in base 2 to the power of (8*sizeof(type)) */
+         type  *number;   /* dynamically allocated memory for number */
     } bignum
 ```