fixed readme

Readme.md

-##Readme for Grammar Generator Prototype Version 2
+#Readme for Grammar Generator Prototype Version 2
 
 This is a much more simplified version of the original
 grammar-generator prototype (which is in the mk1 branch).
 
-#Build:
+###Build:
 Build using `stack build` which should install all the dependencies
 and use ghc to compile the source files in the src directory.
 
-#Run:
+###Run:
 The executable produced is `gg-mk2`, which takes a filename
 as input. Running `stack exec gg-mk2 file.ast` will run the
 grammar generator with the AST specified in the given file.