Close gocode Daemon When Package Is Deactivated

[IngCr3at1on]

Per discussion on slack:

Add hook to shutdown gocode daemon and update it if package is deactivated.

Should solve issues with autocomplete failing after Go updates.

[joefitzgerald]

The update portion is orthogonal, but will be achieved via some hooks in the go-get package. I don't think we want to prompt people to upgrade gocode every time the package is deactivated (i.e. every time you close a window).