Use mvim as git's default editor.

This is simply because my box's vim executable started behaving weirdly.
Some upgrade broke it, I suppose.
Add literate coffeescript support and clean-up.

The syntastic dub package location strategy is now merged into its
source, so there's no need for my own monkey searches.
Fix redundant PATH concats in the zshrc.

I was appending cabal/haskell paths twice (at both head and tail) to my
PATH variable. This fixes that.
Ditch fetching all github pull-requests by default

This turned out to be quite a bore.