Revert "Removed Google Kix (Google Docs) support"

This reverts commit 24b2955154a13cac8aa7d6e601c55956133bea47.

Conflicts:
	CHANGELOG
	content/avim.js
Fixed Google Docs support

Basically we’re back to f55e9c4337baf9c4eb29329f41f8617b4d5630fc in terms of functionality. Pasting synchronously no longer works, even inside a composition, so resort to pasting on a zero-second timeout. Still some wonkiness with tables and Google Slides.

Fixes #21.