Wrote body for s:parse_options to allow users to specify config options
to the Bundle command. The most common use for this would be to set the
path to a plugins runtime files directory. If a plugin repo stores it's
runtime files in a subdirectory, you need to be able to specify the path
to this directory in order to laod the plugin. For exmaple,

" exvim stores runtime files in subdir of repo root
Bundle 'jwu/exvim' 'rtpath=./vimfiles'

The parser will read arbitary options, but currently only rtpath is
used.

- also work in batches

- having it as a function makes it slower

- as `http` one just redirects to `https` on GitHub

- use `let g:vundle_default_git_proto = 'git'` to set default protocol
to build URIs to clone from

- "transcient bundle" - a bundle installed with :BundleInstall or interactively
  without being declared in .vimrc

- treat them the as if they were configured
- so everything works the same

- ie before this change helptags weren't generated automatically
  with `BundleInstall bundle` or with interactive mode

- it changes the way `:BundleClean` works, since it removes directories
  that aren't bundles
- FIX: `:source .vimrc` to let `:BundleClean` remove transcient bundles

- closes #99

- closes #110

Uris for repos specified as user/repo end up being https://github.com/user/repo. For some reason, github allows cloning from such uris, however, it is better to rely on the addresses that github provide for cloning, and those include the trailing .git

This change appends .git to github repo uris when needed.

- otherwise it defautls to vim-scripts repos
- closes #69
- TODO: pass options aswell

- closes #37
- join is useless there

GitHub usernames cannot start with an underscore, but they can be a
single character long.

- ie, like this
Bundle 'gmarik/vundle'

- this was intended for case when user uncomments installed `Bundle` and
reloads .vimrc; which should make the bundle available
- TODO: later

- fixes https://github.com/gmarik/vundle/issues#issue/3
- TODO: not the most efficient approach

- so it's ready to use right after installation

- vundle.vim - entrypoing and loader
- config.vim - configuration and runtimepath management
- installer.vim - installation and docs