FIX: `coffee-mode` uses `coffee-tab-width` instead of `tab-width`.

And recently it has removed `tab-width` dependency completely.
Merge pull request #493 from pokehanai/hotfix/coffee-tabwidth

FIX: `coffee-mode` uses `coffee-tab-width` instead of `tab-width`.
Merge commit '39f95c16c57dcf8dece1934bc2fa8e39e9fc5d0f'

* commit '39f95c16c57dcf8dece1934bc2fa8e39e9fc5d0f':
  FIX: `coffee-mode` uses `coffee-tab-width` instead of `tab-width`.