Update Gradle Wrapper to v1.12 and update Groovy to 2.3.1
Merge pull request #54 from kaendfinger/master

Update Gradle Wrapper to v1.12 and update Groovy to 2.3.1
tweaked EnvPropagateSpec
replaced "invoke a server" with "start a server"
Add new client written by golang

The current build configuration is temporary. It will be thoroughly restructured.
Pass all tests fo golang client event in windows
Amend a way of integration test thoroughly