Fixed prompt for when git repo is dirty.

Git changed it's output for determining when a working directory is clean.
(via rmm5t)
Added Ruby performance boosts.

via rmm5t
Removed gemrc from git index.
Added gemrc to .gitignore.
Added global gitignores for rbenv and pow.
Removed an old, unused require in irbrc.
Moved my IRB helper methods into their own ruby files.
Added Mike Clark's source_for helper method to my IRB utils.
Added documentation to .gitignore.