fixed command subscriptions not remove.

Hello,
I fixed command subscriptions not remove when disable the package.

When I disable `autocomplete` then enable it. Then toggle autocomplete view. The command function was be execute twice, because the command subscription didn't remove.
![2014-07-23 10 18 12](https://cloud.githubusercontent.com/assets/1680868/3674418/7e857950-1276-11e4-832e-67f298632e84.png)