pip commited as a single commit

[aalexanderr]

I'm creating this issue to try understanding the decisions & plans here:

• was there any reason pip was committed without use of git features like subtree/submodules (or even google's repo)?
• whole pip is committed to the repository, while only pip._internals.vcs package is used. is there plan to use more of pip pkgs? or is pip's vcs module waiting to be refactored for fetchcode and the rest of pip will removed?

[aalexanderr]

closed in favor of #68