Tweak the slate grid configuration

So that it offers slightly more granular control.
Fix precedence of the `~/.bin` dir in `$PATH`

By moving the addition of `~/.bin` to the `$PATH` to the bottom of the
`.zshrc`, we ensure it'll take precedence.
General vimrc update

- Adds/removes plugins
- Adds key bindings for quickly opening a browser with a Google query
- Adds a binding to send `:reload` to `ghci` REPL with `vim-slime`
- Removes tab management key bindings which didn't make sense and
  conflicted with `t`
- Adds support for rendering comments in italic on the terminal
- Disables Syntastic checks when opening files and makes haskell a
  passive filetype for it
- Changes snippet expansion key bindings (they now work on iTerm!)
- Makes Syntastic aggregate errors from different syntax checkers
- Disables vim2hs enumeration conceals (the annoying `deriving(..)`
  things)
- Makes `tagbar` tag generation more reliable with `hasktags`
- Changes our colorscheme (again!)
- Uses the super-cool new smartcase option (vim >= 7.4)
- And *most* importantly, add `codex.tags` to as a tags source for
  haskell (generate tags with `codex update` - this is the best thing to
  happen to Haskell programming tail-recursion)
Add cabal-vesrion script

To easily fetch the latest version of a cabal package.