Mass fixes to headers in README.md files

There were many many README.md files with the wrong heading level for
different sections. These have been changed.

To help go through the changes it should be noted I used sgit and also
here is what is changed:

The 'Try', 'To build' and 'To run' lines have two '#'s. Some had one and
others had three.

An exception is that in 1984/anonymous/README.md for the alternative
code that had three '#'s. This is not consistent yet and it might be
that only two are desired. But for now that one at least has three.

2013/cable3/README.md

@@ -3,13 +3,13 @@
     Adrian Cable  
     <adrian.cable@gmail.com>  
 
-# To build:
+## To build:
 
 ```sh
 make
 ```
 
-### To run:
+## To run:
 
 ```sh
 ./cable3 bios-image-file floppy-image-file [harddisk-image-file]
@@ -27,7 +27,7 @@ some implementation of SDL1 also has this problem. Thank you Cody for your
 assistance!
 
 
-### Try:
+## Try:
 
 ```sh
 ./runme
@@ -111,7 +111,7 @@ PLEASE NOTE that under UNIXes the keyboard must be in raw mode for the emulator
 	./cable3 bios floppy.img harddisk.img
 	stty cooked echo
 
-### To run the emulator - floppy mode only
+## To run the emulator - floppy mode only
 
 The simplest use of the emulator is with a single floppy boot disk image, like the fd.img provided, which is a FreeDOS boot disk.
 
@@ -121,7 +121,7 @@ Before running the emulator on a Unix-type system, stty needs to be used to put
 	./cable3 bios fd.img
 	stty cooked echo
 
-### To run the emulator - floppy + HD mode
+## To run the emulator - floppy + HD mode
 
 Easiest to start with is to try a ready-made 40MB hard disk image containing a whole bunch of software: