Revert "Merge pull request #674 from mgedmin/fix-sys-path-better"

This reverts commit 920d7c71d800ba4c0da8fcac605cdf0adfe46f3a, reversing
changes made to 23e66c9429b8f51046e4efc0ab39b633254d3053.
revert "Merge pull request #648 from nvie/develop"

This reverts commit 73d46a83f6b26155398310d8dfd251015c751030, reversing
changes made to 860b4149b9c4ff4c1b66ff554150aaf9d4bc071f.
Merge pull request #690 from dstufft/undo-things

I hate computers.