progress on VM
some fixes to apyc.h
Added constants and moved code generation machinery into VM

- Made global constant VM
- Renamed the runtime VM to SM (stands for Stack Machine)
- Made constants to refer to runtime data structures during compilation
- Moved simple hello world code generation into emitRuntime in
  VirtualMachine
deleted extraneous comments
revised emit, added comment outputs, docstrings
some fixes to previous commit
tabs -> spaces
removed RETURN_ADDR vector
fixed emit for compare. also, vm has separate write method now
renamed emitComment, write -> comment, code
added function prologue, epilogue, fixed calls
it seems I accidentally the Makefile
added suppose for calling native C++ functions
abstracted code emit for COMPARE into helper function
fixed emit(int)
added basic runtime test, fixed various issues with emit
fixes/sample runtime code gen example
added newline function for convenience
added keyword for setting up function
removed code for emitting comparisons