Slight change in 'greater challenge' line

In the line in README.md and index.html files that said:

    ### NOTICE to those who wish for a greater challenge

I added a ':' at the end of the line.

There were some entries that had a link fix in the index.html file but I
only looked up through 1995/leo as those still have to have a 'look and
feel' check and it would just slow things down.

1989/paul/README.md

@@ -41,7 +41,8 @@ better debugger or trace could easily be added.
 
 ## Judges' remarks:
 
-The author's comments is a detailed program explanation, if you wish to learn more about the obfuscation method used.
+The author's comments are a detailed program explanation, if you wish to learn
+more about the obfuscation method used.
 
 
 ### Historical note:
@@ -54,7 +55,7 @@ However as this is no longer a problem the trailing `\` has been restored in all
 versions, both the original and the fixed for modern systems version.
 
 
-### NOTICE to those who wish for a greater challenge
+### NOTICE to those who wish for a greater challenge:
 
 **If you want a greater challenge, don't read any further**:
 just try to understand the program via the source.

1989/paul/index.html

@@ -420,14 +420,15 @@ better debugger or trace could easily be added.</p>
 <h3 id="alternate-use">Alternate use:</h3>
 <pre><code>    ./paul.alt</code></pre>
 <h2 id="judges-remarks">Judges’ remarks:</h2>
-<p>The author’s comments is a detailed program explanation, if you wish to learn more about the obfuscation method used.</p>
+<p>The author’s comments are a detailed program explanation, if you wish to learn
+more about the obfuscation method used.</p>
 <h3 id="historical-note">Historical note:</h3>
 <p>The original source contained a long line which caused many mailers to barf.
 The original file may be re-constructed by removing the trailing <code>\</code> on line 12
 and joining lines 12 and 13 together without a space.</p>
 <p>However as this is no longer a problem the trailing <code>\</code> has been restored in all
 versions, both the original and the fixed for modern systems version.</p>
-<h3 id="notice-to-those-who-wish-for-a-greater-challenge">NOTICE to those who wish for a greater challenge</h3>
+<h3 id="notice-to-those-who-wish-for-a-greater-challenge">NOTICE to those who wish for a greater challenge:</h3>
 <p><strong>If you want a greater challenge, don’t read any further</strong>:
 just try to understand the program via the source.</p>
 <p>If you get stuck, come back and read below for additional hints and information.</p>