Added cocos2d 2.1-rc1 podspec

New version of cocos2d added, plus fixes FileList and "The version should be included in the Git tag." warnings.

Based on previous podspec. Validates and works for me, but my first podspec. Also unsure of the change in versioning (from 2.1.rc0 to 2.1-rc1, dot to dash) to remove the "The version should be included in the Git tag." warning causes any issues for people updating.