Add a magical extract function

Calling "extract" in bash automatically determines the filetype and
extracts the archive. The following archives are supported:

tar.bz2, tar.gz, bz2, rar, gz, tar, tbz2, tgz, zip, z, 7z
Add automatic code folding

vim auto folds code (to 2 levels max). Also, add a shortcut to
fold/unfold code by simply hitting the spacebar.
Plugin to easily rename files in vim

To rename the current file, :Rename[!] can now be used.