Load the bundled dependencies if we want to run the iridium command from the git repo

Use case: I want to play with the edge version of iridium, which i have cloned in ~/src/iridium.

Running this
  $ ~/src/iridium/bin/iridium generate app my_app
did not work, because iridium could not find its dependencies. This fixes that.

Inspired by rails/railties/bin/rails