remove trailing blanks in markdown files

We used this command to find markdown files with trailing whitespace.

```sh
find . -name '*.md' -print0 | xargs -0 grep -E -l '[[:space:]][[:space:]]*$'
```

After removal, we did a `make www`.

2012/deckmyn/deckmyn.md

@@ -1,4 +1,4 @@
-# USER MANUAL 
+# USER MANUAL
 
 
 ## Calling the program

2012/hou/hint.html

@@ -120,12 +120,6 @@
 <!-- END: this line ends content from: inc/before-content.default.html -->
 <!-- START: this line starts content for HTML phase 21 by: bin/pandoc-wrapper.sh via bin/md2html.sh -->
 
-<h1 id="most-useful-obfuscation">Most useful obfuscation</h1>
-<p>Qiming Hou<br />
-<a href="mailto:hqm03ster@gmail.com"
-class="email">hqm03ster@gmail.com</a><br />
-<a href="http://www.houqiming.net"
-class="uri">http://www.houqiming.net</a></p>
 <h2 id="judges-comments">Judges’ comments:</h2>
 <h3 id="to-build">To build:</h3>
 <pre><code>make hou</code></pre>

2012/hou/hint.md

@@ -1,10 +1,3 @@
-# Most useful obfuscation
-
-Qiming Hou  
-<hqm03ster@gmail.com>  
-<http://www.houqiming.net>  
-
-
 ## Judges' comments:
 
 ### To build:

2012/kang/README.md

@@ -72,7 +72,7 @@ echo uno | ./kang.alt
 What does it get right? What does it get wrong? How does it compare to the
 original entry without the change of `f` to `v`?
 
-Finally why does it get wrong what it gets wrong? 
+Finally why does it get wrong what it gets wrong?
 
 
 ## Judges' remarks:

2012/omoikane/README.md

@@ -7,7 +7,7 @@ make
 There is an alternate version that will read from the compiled file itself, in
 case you don't have a `/dev/urandom` file. There is also a version that should
 theoretically work with Windows which distinguishes binary and text. See
-[alternate code](#alternate-code) below. 
+[alternate code](#alternate-code) below.
 
 
 ## To use: