Update 1992 winning entries' README.md files

Format and typo fixes.

1992/nathan/README.md

@@ -13,7 +13,7 @@ UK BS12 4SQ
 make all
 ```
 
-## To run
+## To run:
 
 ```sh
 ./nathan
@@ -84,7 +84,7 @@ re-distribute a program contest winner to the network!
 
 ## Author's remarks
 
-### PROGRAM USE:
+### Program use
 
 This program is a hello world text encryptor/decryptor. It uses an
 enigma (I think) style encryption algorithm, where the encryption
@@ -100,7 +100,7 @@ before the key. (Actually encryption and decryption proper inverse
 operations, so you can use decrypt to scramble and encrypt to
 descramble, if you're perverse.)
 
-### PORTABILITY (A little knowledge is a dangerous thing):
+### Portability (A little knowledge is a dangerous thing)
 
 It's written in ANSI C, and doesn't even assume an ASCII character
 set, (it has an array of the characters to convert), so should be
@@ -116,7 +116,7 @@ another scoping level does not need to be opened.
 Being an encryptor/decryptor, you probably want the source code to
 be obfuscated, to hide the algorithm.
 
-### OBFUSCATION:
+### Obfuscation
 
 In spite of the fact that it looks like a nice friendly hello world
 program, it isn't (as documented above). (Short lines have been padded,