Upgrade to MongoDB 2.6.0

- All unit test passed but still running Mongo Java Driver 2.11.4
Upgrade to MongoDB 2.6.1

- All unit tests pass
Test whether the river handles TokuMX oplog refs properly
Handle TokuMX oplog refs
Don't print full contents of large objects to logs, in Slurper
Merge pull request #273 from kdkeck/tokumx-refs

Handle TokuMX oplog refs