Remove doublewrite on collectionview edit cell

@gterrono - when we were doing the rewrite, you couldn't replicate this bug.

To replicate: take the current live version with a demo app.  In the collection view, double-click on a cell, and edit the cell (let's say it used to say "A" and you make it say "B").

**Expected**: the cell now says B, and the database updates accordingly.
**Actual**: the cell now says B. After a few seconds (DB returns) the cell says "BB".  When you refresh, it says "B" again.

After this change, everything works as expected.

As a bonus, pressing enter when finished editing a cell also now does the right thing.

### A bit of technical detail:
I moved our collection update meteor methods into their own place in ./lib.  As a result, when we send an update, it now happens immediately (using roughly the same trick as Meteor's latency compensation).