Spell-check Markdown by type, not file extension

Previously, only `*.md` files would get spell-checking. This change adds
`*.markdown` and decouples Markdown spell-checking by file extension.

http://robots.thoughtbot.com/vim-spell-checking/
Disable Rubygem documentation to make Bundler fast
Update Giant Robots blog post URLs in README
Only try to install vundle if it's not installed

Prevents error on re-running ./install.sh:

    fatal: destination path '~/.vim/bundle/vundle' already exists and is
    not an empty directory.

https://github.com/thoughtbot/dotfiles/issues/195
skip linking LICENSE file during install
Use rcm instead of ./install.sh

The rcm suite is designed to replace the `./install.sh` script found in
this and many other dotfiles repos across GitHub. By using rcm users can
combine multiple dotfiles repos, tag dotfiles, have host-specific
dotfiles, and other powerful features.

This commit removes `install.sh`, updates the README, adds a post-up
hook that vundles the vim bundles, and adds a `rcrc` configuration that
ignores `README.md` and `LICENSE` and sets the dotfiles directory to
just `dotfiles`.
Always update from vundle

Previously, the after-up hook would only do a `:BundleInstall` when
installing vundle for the first time. This is inconsistent with the
pre-rcm process, and also less convenient.
Cleanup zshrc

* remove duplicates with zlogin
* order by functions first, then bindings, then exports
* lowercase `setopt` arguments for consistency with `setopt` output
Use Brewfile
Correctly link to rcm in README
Use thoughtbot/rcm in Brewfile
Add rbenv shims and trusted binstubs to PATH

Our expected way of managing Rubies is with rbenv:

https://github.com/thoughtbot/laptop/blob/master/common-components/ruby-environment

This commit loads rbenv in `zshrc` as recommended by the rbenv docs:

https://github.com/sstephenson/rbenv#basic-github-checkout

Assuming the binstubs for a project are in the local bin/ directory, we
can even go a step further to add the directory to shell $PATH so that
rspec can be invoked without the bin/ prefix:

    export PATH="./bin:$PATH"

Doing so on a system that other people have write access to (such as a
shared host) is a security risk:

https://github.com/sstephenson/rbenv/issues/309

The `.git/safe` convention addresses the security problem:

https://twitter.com/tpope/status/165631968996900865

This zsh fix may be necessary for OS users in order to fix a bug:

https://github.com/thoughtbot/laptop/blob/master/mac-components/zsh-fix
Complete parity commands like heroku

Adds tab completiong to `production` and `staging` which acts as tab
completion to heroku.
Add psqlrc
Update copyright to 2014
changes 'brew tap thoughtbot/rcm' to 'brew tap thoughtbot/formulae'
Don't assume location of zsh
Use local zlogin config if present
Resolves #216 - adds note about ensuring user is in Clone/Fork root before 'brew bundle' is run.
Added syntactical clarity to instruction to change directory.