Add solarized themes for iTerm2

Both solarized dark and light are now included in the subdir
iTerm2. They are copies from the original repo because it doesn't
seem worth to clone a ~10Mb repo just to keep in sync 2 files,
considering that solarized hasn't changed much in the past years.

The rakefile has been updated to trigger the automatic installation
of these two themes only if OS == OSX. The user will still have
to set the themes for his/her current profile manually (but that's
explained at the end of the installation process).
Merge pull request #259 from duhanebel/iterm_solarized

Add solarized themes for iTerm2
Remove all vim submodules
Add bundle to .gitignore

Bundles are now handled via Vundle so there's no need to monitor
the bundle directory as everything is done through the :Bundle
command
Change vimrc to use Vundle instead of pathogen
Move mapleader definition to vimrc

It seems that the mapleader has to be defined before vundle starts
to load the plugins. For this reason, I moved it from yadr-keymap
back into the vimrc. I'm sure it's not a big deal having the leader
mapped under the "general config" instead of inside settings.
Remove csapprox

Since we're now able to install Solarized on iTerm2, there's no
need for approximating the theme when using vim instead of
mvim. In fact, using csapprox on iTerm2 with solarized installed
breaks the theme completely.
Update Rakefile to manage pathogen-to-vundle upgrade

The Rakefile now detects if pathogen is installed and in that case
it performs the following operations:
1. Moves vim/bundle to vim/bundle.old
2. Removes all the submodules from git config and cache
3. Initializes and updates the new submodules (zsh and bundle)
4. Runs the vundle installer that takes care of the rest
Update yadr's binary to support Vundle

yadr-vim-add-plugin now supports adding vundle plugins
Add yadr command line tools to remove/list plugins

Two new command line tools: yadr-vim-remove-plugin and
yadr-vim-list-plugin do what they're supposed to.
Update zsh alias to support new yadr's commands

yrv -> deletes plugin
ylv -> lists plugins
Change rake file to reuse methods in vundle.rb

Vundle::update_vundle can be reused inside the Rakefile
Fix a bug that was preventing a clean install

The installation of the plugin only happened during an update
because the code that checks out the vundle plugin was in the
wrong place.
Fix a bug that was causing rake to overwrite SHELL settings

The prezto install procedure now checks to make sure the user
doesn't have an alternative version of zsh installed before changing
the current shell preference with "chsh".
This may be the case when an user is already using zsh but on a
different version from the one shipped with OS X

Fixes #264
Merge pull request #265 from duhanebel/zsh_install_check

Fix a bug that was causing rake to overwrite SHELL settings
Fix a typo on the Rakefile
Fix a bug that's causing the installer to overwrite backup files

When rake install/update is run for the second time, any .backup
file created by the first run it's going to be overwritten by
the new symlink even if the current file is the same as the one
we are going to write.

The rakefile now checks if the symlink we are going to create
points to the same target as the one already there and if that's
the case, doesn't overwrite any backup.
Change duhanebel's forked repos to originals

Both powerline and syntastic on the default vundles.vim were
pointing to my own forks, which are not needed for the main repo.
fixes #268
Merge pull request #268 from chadkouse/env_shell

"uninitialized constant SHELL" in zsh install step