libgit2 creation methods have name collisions with internal V8 functions #271

The classes and structs that have creation methods in libgit2 (e.g. git_revwalk_new) will have their methods reduced to just New which is a name collision with an internal method. Either we rename this method or rename these methods to be something else. Maybe turn git_revwalk_new into Create or CreateRevwalk. The latter will retain backwards compatibility but is a little redundant.

Thoughts?