.osx: Kill `cfprefsd` after changing preferences

As of OS X 10.9 this is necessary to make sure the changes persist.

Closes #330.
add GOPATH into export
Merge branch 'master' of github.com:mathiasbynens/dotfiles

* 'master' of github.com:mathiasbynens/dotfiles:
  .osx: Kill `cfprefsd` after changing preferences