make contributing.md generic and add testing.md
Merge pull request #318 from nodegit/contributing

Make contributing.md generic and add testing.md
Rename TESTING.MD to TESTING.md
Fixed fetch to be async and use callbacks
Fixed tests and reimplemented missing functions on Repository
Added in optional ignore cert param for fetching
Set a higher timeout for the fetchAll test
Merge pull request #319 from nodegit/fix-fetch

Fixed fetch to be async and use callbacks
make Repository.initExt normalize options
add test for initExt