Merge pull request #28 from SonarDesignInc/develop

Mongo compiles and tests run again since recent language changes
Updgrade for Dart SDK version 0.5.13.1_r23552
v0.1.20
config to look at sonar repo - do not merge back
Merge branch 'sonar' of github.com:SonarDesignInc/mongo_dart into sonar