allow disabled packages to be installed
:lipstick: Remove code duplication around emitting events

There was code in a number of places that formatted the event names
differently depending on whether the event was for a theme or a
package. This change creates an `emitPackageEvent` method that
standardizes the logic for determining if the event is for a package
or a theme and emits the properly formatted event.

Caveat: It makes searching for the source of a given event more
difficult.
Merge pull request #139 from atom/iz-install-disabled-packages

Allow disabled packages to be installed, take 2
Prepare 0.120.0 release
Fix ternary operator and parameter passing
Compress assignment of theme into one-liner
Merge pull request #140 from lee-dohm/emit-cleanup

:lipstick: Remove code duplication around emitting events
Prepare 0.121.0 release