Fix: "python ABS/PATH/TO/ipython.py" fails

The following line in setupbase.py was the problem.  It assumes
that your CWD is always at the repository root.  This patch removes
this assumption.

    execfile(pjoin('IPython','core','release.py'), globals())
Merge pull request #3276 from tkf/fix-setupbase

Remove assumption that setup is being run from repo root.