Fix error on this.removed during session shutdown.

Followup to 4f4e5342 which removed session resumption. That commit
deferred the _deactivateAllSubscriptions call on session shutdown, but
left around the immediate deletion of the merge box
state (collectionViews). This meant that if any publish callbacks were
called before the _deactivateAllSubscriptions call, they would operate
on the invalid collectionViews state.

This change ensures that the subscriptions are considered deactivated as
soon as we decide to deactivate them, even before we actually deactivate
them (and call their possibly-yielding stop callbacks).
Update fibers instructions in README.

Now it matches the instructions in the docs.

Fixes #1519.

(All of this is a mess; we should stop using the dev bundle in
deployments entirely.)
Fix test added in dcfd00f.

The client version was running non-existent methods (because the
collection didn't exist server-side); because no callbacks were provided
to insert or update, this resulted in a Meteor._debug, but no failure.
facts: proof-of-concept server-side statistics.

Publishes statistics from the server to a Minimongo collection,
Facts.server. (On the server side, Facts is *not* backed by MongoDB.) By
default, this is available to all users if autopublish is on, or no
users if it is not on, but you can configure this with
Facts.setUserIdFilter.

You can add an ugly view on the stats to your app with {{> serverFacts }}.

Current stats, by package:

- mongo-livedata:
  - observe-handles
  - live-results-sets (when this is less than observe-handles,
    cursor de-dup is helping you)
- livedata
  - subscriptions
  - crossbar-listeners
  - sessions
More history updates.
Add comments in deps linking to the docs
document predicate signature in restrictCreationByEmailDomain
Use object equality for closing connections for tokens.

Fixes #1540.
Merge branch 'devel' into follower