Add cask for Google Drive
Merge pull request #325 from moul/google-drive

Add cask for Google Drive
use absolute path to ln when linking

this is an attempt to avoid GNU `ln`, which is sometimes installed on
macs by users sick of dealing with the subtle differences of BSD tools
from the rest of the known universe.

refs #328
bump version to 0.12.1
whoops! pass down force argument to installer

this was preventing the `brew cask install --force cask` syntax from
working

the test was wrong too - corrected that so now we're covered from future
breakage

refs #329
bump version to 0.12.2
added link line to spectacle