Fix heading level of 'Try' section

It was agreed to be '## Try:' but there were many files where it was
'### Try:'. This has been corrected.

2015/muth/README.md

@@ -12,7 +12,7 @@ make -B [MACHINE=your_machine.h] [TAPE=your_tape.h] [X=[0|1|2|3|4|5|6|7|8|9]] [V
 ```
 
 
-### Try:
+## Try:
 
 ```sh
 ./try.sh