Adding some doc comments

Hey,

I was adding some doc comments. Going through the code, I have fixed a few PSR inconsistency.

Some of the things I noticed are

1 ) PackageXmlParser and 2 ) PackageJsonParser have a different api. 

In one you are expecting a directory path, in the other you expect the .json path. I feel it is worth to change.

Also the gitIgnoreFiles method seems spread, seems some sort of refactoring is good.

Thanks
if you don't have anything useful to put in the description, it is better to omit it IMO