Don't deactivate when given nonexistent virtualenv
Export WORKON_HOME so other programs can see it

I have a little mkvirtualenv script that wants to read this.
Ack should search "config files"
New @{upstream} git aliases

Also expanded my diff stat aliases because "!git ds" is not much
shorter than "diff --stat", and I also bet that Git's bash_completion
stuff might find it easier to complete when I define aliases using Git
subcommands rather than shell commands (but I didn't bother to test
this hypothesis).
Remove unnecessary "git spush" alias

Turns out it's enough just to have the executable git-spush in your
path, which I do (in ~/bin).
A few more Vim add-ons
Vim configuration for shell scripts