Update phinze/cask to caskroom/cask

It triggered this warning if brew cask had already been upgraded
to caskroom/cask and we ran rake:

> Warning: Could not tap phinze/homebrew-cask/brew-cask over
> caskroom/homebrew-cask/brew-cask
Merge pull request #155 from slam/caskroom

Update phinze/cask to caskroom/cask
Clarify our position around adding new features to maximum-awesome.
Update homebrew install url

I got the following output after trying to install maximum-awesome on a machine without homebrew.

$ rake

-- Homebrew --------------------------------------------------------------------
Whoops, the Homebrew installer has moved! Please instead run:

ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

Also, please ask wherever you got this link from to update it to the above.
Thanks!

-- Homebrew Cask ---------------------------------------------------------------
sh: brew: command not found
sh: brew: command not found
Failed to tap caskroom/homebrew-cask in Homebrew.
Merge pull request #175 from vinnyliao/patch-1

update homebrew installer url to https://raw.githubusercontent.com/Homebrew/install/master/install
vim-commentary was complaining that \\ was deprecated and to use gc
Merge pull request #177 from josephndenton/readme-fix-gc

vim-commentary was complaining that '\\' was deprecated and to use 'gc'
Merge remote-tracking branch 'upstream/master'