First pass text for oplog tailing in History.md.
Handle modifications to EJSON custom types

OplogObserveDriver cannot try to directly apply these
representation-level mutations; it needs to get the entire custom type.

This implementation is overly conservative, but in practice
Meteor-originated writes shouldn't mutate EJSON custom types
anyway (they should treat them as atomic).
Avoid 100% CPU in tailing during Mongo failover
Apply patch to node versions 0.10.22 and 0.10.23.

0.10.23 just came out and hasn't made any changes to the streams
stuff we patch.
Take out check that can fail during failover
A few History tweaks