Expose WriteResult to callers of DAO.update

Make Mongo's WriteResult available to callers when doing query-based updates.
This allows them to determine things such as the number of rows modified by
an update.
Upgrade to sbt 0.12.1
Add stackoverflow tag to copyright, about
Replace post pom processor that was correcting the type of the casbah dep in the salat-core pom with pomOnly fix from https://github.com/harrah/xsbt/issues/501
Make MissingTypeHint smarter about map-like things
Update Travis CI config to use sbt-extras runner.
Travis CI config now explicitly declares dependency on mongodb service
Bump logback version to 1.0.7
Added support for transforming Map[String, _] or Iterable[Map[String, _]] to a compact JSON string
Rename JSON map support
Switch JSON AST from lift-json to JSON4S
Added BitSet support to DBO, JSON
Bug fix on Long extraction from JInt objects (when using fromJSON and transforming into a case class).
Added a spec in the tests: LongSpec.
Merge pull request #61 from alexandreagular/bug-fix-long-parser

Bug fix on Long extraction from JInt objects
Merge pull request #46 from varju/return-write-result

Expose WriteResult to callers of DAO.update
Return WriteResult from save, remove, removeById, and removeByIds
Update scaladoc
Merge pull request #62 from varju/return-write-result-everywhere

Return write result everywhere
Fix travis.sh to build the scala version matrix
Merge pull request #63 from gildegoma/fix-travis-matrix

Fix travis.sh to build the scala version matrix