Google Docs: Letters in adjacent words treated as dead keys

Typing a new word beginning with “d” after “định” turned “định” into “dịnh”.
Google Docs: Handle normal characters too

KixProxy.commit() inserts text asynchronously, so funnel all input through it to ensure proper order. This commit should be reverted in the event commit() is made synchronous again.

Fixes #64; fixes #77.