Failing Mongo Specs due to error message changes.

[farmdawgnation]

MongoDocumentExamplesSpec and MongoDirectSpec are currently failing under Mongo 2.6 on my local machine with the following failure (or some variation thereof)

'insertDocument :: caused by :: 11000 E11000 duplicate key error index: lift_mongodirectspec.testCollection.$name_1 dup key: { : "MongoSession" }' doesn't start with 'E11000 duplicate key error index' (MongoDirectSpec.scala:234)

It looks like this is caused by Mongo changing their error messages to be more informative. We should update the spec to be a contains check instead of a starts with check.