Use Cask to trigger tests (and solve dependencies)

Follow up from the discussion https://github.com/haskell/haskell-mode/pull/370#discussion_r20136791

Use:
- Install Cask -
http://cask.readthedocs.org/en/latest/guide/installation.html
```sh
curl -fsSL https://raw.githubusercontent.com/cask/cask/master/go |
python
```
- Trigger tests:
```
make check
```
This will use cask only for the tests target.
Improve readability with mocklet binding
Tryout - Make ci work with cask