Ignore .python-eggs directory

Digging around a bit, this looks to be a cache for something called
psutils, which in turn (`mdfind psutil`) seems to have something to do
with zsh.
Revert "Configure hooks and aliases for git commit signing"

This reverts commit 58d6942b4ce2d7e4e25ca435575a7f4bd95dc37a, until
such time that first-class support for automatic commit signing is
added to git (i.e. a `git config` option, or perhaps the proposed
--gpg-sign patch described at [1]). The key problem is that there is no
way to automatically (re-)sign commits during a rebase. This means that
for those who rebase often, manually re-signing is necessary (which is
prohibitively tedious), or one ends up with a patchy history of some
commits being signed and others not.

[1]: http://comments.gmane.org/gmane.comp.version-control.git/240987