Enable `double_click()`, `right_click()`, and `drag_and_drop()` to Firefox driver. Refs #206
Merge branch 'issue-206' of github.com:cobrateam/splinter into issue-206
Merge branch 'master' of github.com:cobrateam/splinter into issue-206
Merge branch 'master' of github.com:cobrateam/splinter into issue-206
Merge branch 'master' of github.com:cobrateam/splinter into issue-206