Fixed two blocker issues that kept the OpLog util from functioning:

1) The pattern match on input wasn't looking at the typeCode field, so all matches failed.
2) It turns out that Master/Slave does *not* include an OpID; therefore, made it Option.

It's hard to rig a test for this as it requires a lot of functional
interactions and a local replica set / master slave. Manually verified &
test forthcoming.

TODO: Subtypes of OpLogEntry for RS vs. Master/Slave?
Register the core Serialization helpers only once

If the trait Implicits is used with short lived objects the overhead of re-registering the helpers becomes quite large.
Documentation fixes SCALA-122
Updated to scala 2.10.3
Updated travis build to include 2.10.3 & 2.10.2
Updating version to 2.6.4
Updated travis.yml
Merge branch 'master' into 2.7

Conflicts:
	project/CasbahBuild.scala
Updates to the changelog
Casbah WriteConcern's `valueOf` now returns an Option (SCALA-127)
Updated changelog in regards to SCALA-103

The update was done with SCALA-101 and SCALA-112
Fix typos in docs refs pr #65
Support Aggregation for MongoDB 2.6

* Added support for Aggregation returning a cursor `AggregationCursor` (SCALA-117)
* Added support for `allowDiskUsage: true` to the top-level of an aggregate
  command with the AggregationOptions helper (SCALA-128)
* Added support `$out` aggregation pipeline operator (SCALA-130)
Fix race in tests
Add helper for explain on an aggregate command (SCALA-132)
Check query failure exception test (SCALA-133)
Code cleanups
Server automatically abort queries/commands after user-specified time limit (SCALA-118)
Update query_dsl.rst
Removed erroneous toInt