Enumeration Correction in C-Interface

Following issue #144.
@alikh31 I have just noticed this has been already fixed by @abtris (and unfortunately cherry picked into master by @pksunkara)  – see https://github.com/apiaryio/snowcrash/blame/master/src/CBlueprint.cc#L104

Please rebase your fork's branch on top of the actual (upstream) master and this diff should go away. 

With that being said – I think the additional test should still be in place – testing multiple resource groups.