Move all generators-related code to their own module
Move the content of "common" to the root of the module
Remove indentation system from generators
Move `write_enum` implementation to the `generators` module root
Move write_type_aliases into module root
Add gl_generator/target to .gitignore
Fix all bugs introduced in the current PR
Now using global functions in static generator
Now using global functions in struct generator
Now using global functions in global generator
Add trait for generators
Change order of functions to match the order in which they are called
Remove globs
Remove all warnings when compiling gl_generator
Merge pull request #171 from tomaka/cleanup

Clean up implementation (step 1)
Merge pull request #172 from tomaka/cleanup-2

Clean up implementation (step 2)
Generators are now building AST
Type aliases are now using `quote_item!`
gen_enum_item now returns an ast::Item
to_rust_ty now returns a ast::Ty