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.

1995/README.md

@@ -97,10 +97,10 @@ Dessert: Chocolate torte
 Antipasti: crudites, olives, roasted red peppers, cheese selection
 Salad: Mixed greens with vinaigrette
 Main Course: Spaghetti with tomato sauce containing mushrooms and black olives
-	     selection of hot and mild Italian sausages
+             selection of hot and mild Italian sausages
 Bread: Fresh French bread
 Dessert: Cookie selection, featuring chocolate chocolate chip cookies and
-	 chocolate butter cookies
+         chocolate butter cookies
 
 
 ### Session Three
@@ -108,7 +108,7 @@ Dessert: Cookie selection, featuring chocolate chocolate chip cookies and
 Antipasti: Crudites, olive selection
 Salad: Mixed greens with mustard vinaigrette
 Main Course: Broiled salmon with lemon pepper mayonnaise, chard, mixture
-	of white and wild rices
+        of white and wild rices
 Bread: Cheese bread with herbs
 Dessert: Chocolate cheesecake (Courtesy of Elizabeth Watson)
 
@@ -119,8 +119,8 @@ Antipasti: Crudites, olive selection, roasted red peppers, cheese selection
 Bread: Sourdough
 Salad: Mixed spring greens with flowers, and mustard vinaigrette
 Main Course: Surf and Turf--Grilled steaks of salmon and New York steak
-	grilled vegetables--onions, peppers, portobello mushrooms
-	wild rice
+        grilled vegetables--onions, peppers, portobello mushrooms
+        wild rice
 Dessert: Chocolate mousse
 
 
@@ -142,7 +142,7 @@ Bread: Focaccia with black olives and mozzarella cheeses
 Salad: Mixed spring greens with flowers and mustard vinaigrette
 Soup: Homemade butternut squash soup with mushrooms
 Main Course: Cracked Dungeness crab with lemon mayonnaise, broccoli,
-	mixture of white and brown rice
+        mixture of white and brown rice
 Dessert: Key lime pie
 
 

1995/dodsond1/README.md

@@ -27,7 +27,7 @@ You might consider giving the following input:
     ... a male (who) gets very, very frustrated sitting in a chair all
     the time because males are biologically driven to go out and hunt
     giraffes.
-	    -- Adjunct Professor Newt Gingrich, Reinhardt College, 1/7/95
+            -- Adjunct Professor Newt Gingrich, Reinhardt College, 1/7/95
 ```
 
 ... which can be done like:

1995/leo/README.md

@@ -78,7 +78,7 @@ You take a big sheet of "arithmetic" paper and draw a line
 of length 1 (between 2 crossings) at the center of the sheet:
 
 ```
-				|
+                                |
 ```
 
 This makes 2 open ends (I think the notion of an "open end" doesn't
@@ -123,15 +123,15 @@ Step 4:
 Step 5:
 
 ```
-			  ._|   .   |_.
-			__|  \./ \./  |__
-			   \__|   |__/
-			__./   \./   \.__
-			__I     |     I__
-			   \__./ \.__/
-			__./  |   |  \.__
-			  |_./ \./ \._|
-			    |       |
+                          ._|   .   |_.
+                        __|  \./ \./  |__
+                           \__|   |__/
+                        __./   \./   \.__
+                        __I     |     I__
+                           \__./ \.__/
+                        __./  |   |  \.__
+                          |_./ \./ \._|
+                            |       |
 
 ```
 
@@ -252,7 +252,7 @@ even want to explain what it does. You've been warned!
 
 
 ```
-	    *               *               *
+            *               *               *
 ```
 
 Special thanks: