Correctly declare Python version compatibility.
Ignore dist and build dirs.
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.