Use package schema 2.0

This makes your plugin installable on ST3 (which it seems to work on).

Also, you **haven't pushed a tag in 2 years**. Remember that Package Control looks out for these tags when installing it on a machine.

In order for PC to grab your tag, it must be a valid [semver](http://semver.org). You may optionally use a leading `v`. If you forget to add a tag, Package Control will never see your release!