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?
Merge pull request #63 from bwmcadams/master

Fixed two blocker issues that kept the OpLog util from functioning
Updated changelog and upgrade refs pr/#63
Merge branch 'master' of github.com:mongodb/casbah
Support vargs for as[Type]("Keys"*) (SCALA-134) (pr/#61)

Thanks to Yann Moisan for the initial patch