Add Ruby 2.1.0 to Travis CI configuration
Clearly scope tests for UserDefinedBuilder#build_class
Register included interfaces with the GType system
Extract GType information gathering to a class
Avoid re-registering a registered class
Remove UserDefinedBuilder#find_vfunc
Map interface gtypes to GType objects
Remove ObjectBuilder#object_class
Add test for ObjectBuilder#object_class_struct
Implement InterfaceBuilder#interface_struct
Implement InterfaceBase#to_ffitype
Clean up whitespace
Allow specifcation of vfuncs from interfaces in user defined types
Use markdown for all documentation
Add item regarding derived types to TODO
Update dependency on indentation