Updated vimrc, .gitmodules & railscasts theme

- Added utility functions in vimrc taken from tpope's vimrc
- Updated railscasts theme (my fork) and fixed a lot of issues, merged
  both Josh' (original author) and Nick's (modifier) versions and made
  them more coherent and fixed several term & gui differences.
- Updated update_bundles script to include more of my_forks.