Adds VCS urls support.

Now, requirements, containing VCS urls could be
compiled. During compilation, pip-compile will checkout
sources, get all dependencies and pin spec to exact
repository revision.
Configurable via PIPTOOLS_ROOT environment variable, default is ~/.pip-tools. And attempt to make pip-compile-detailed.t results more stable.
Fixed issue when *.egg-info directory is in unusual place.
Fixed unsuccessful merge.
Fix cram tests to use pip<1.5, because pip compile is not ready for newer pip.
Show logging from pip.
Allow external and insecure sources.
Merge branch 'quick-fix-externals' into my-future
Package manager was fixed to work with latest pip and wheel (this patch requires that two my other branches were also merged: work-with-vcs and quick-fix-externals.