Fixed interpreter.mli
Whitespace
Added Makefile
Removed polymorphic variants from Parser
Exported initial empty environment and removed test code for Interpreter
Fixed lexing rules for numbers, identifiers, and whitespace
Raised lexing priority for keywords
Added example program
Added main module with compiler pipeline
Tell ocamlbuild to use Menhir
Added .gitignore
working: lexing, parsing for expressions, print and set statements