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
the description in the parent class is enough IMO, and this one is wrong anyway, as this command does not archive anything