Merge pull request #5 from SonarDesignInc/master

Compiles again after dart:uri removal
v0.1.5
Merge pull request #6 from SonarDesignInc/master

Fixed warning generated by intx.dart superclass
Added a dateTime getter + test on ObjectId equivalent to mongo shells' getTimestamp
Did not use "getTimestamp" as name as lib already has a class Timestamp and the
return type is just a dart DateTime.