* Add an option for Dart2
* add dart2 samples, update travis
* fix dart installation
* Upper constraints on the SDK version
* Update dependencies
* supportDart2 option can now be passed through --additional-properties
* Update petstore tests
* Update dart2-petstore.sh
* Running tests on Dart VM
* Fixed JSON deserialization bugs
* Fixed missing initialization of postBody
* Run bin/dart2-petstore.sh to regenerate libraries
* Update pom.xml
* Added SDK version constraints in pubspec.mustache
* Run bin/dart2-petstore.sh to regenerate libraries
* move dart2 test to the end
