simplify installation separation for regular vs vcs dependencies
simplify installation separation for regular vs vcs dependencies

We previously divided our dependencies into two separate lists.
This was to allow us to require hashes for pypi packages, but
ignore them for VCS dependencies since they won't exist. Now
that we're installing one package at a time, we can bundle dependencies
back together earlier and reduce the code duplication.

nateprewitt/pipenv,kennethreitz/pipenv