Merge pull request #54 from kaendfinger/master

Update Gradle Wrapper to v1.12 and update Groovy to 2.3.1
fixed a race condition when multiple groovyserver concurrently is started
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
Avoid hard code of package name of groovyserv for AnsiColor#printlnAsTestResult() when testings
Extract a local AnsiColorConsoleLogPlugin with AnsiColor and StopWatch to buildSrc
Tweak groovyclient.go
Tweak build.gradle

- 'natives' -> 'platform'
- split 'compileGo' with 'crossCompileGo'
Add new groovyserver written by go
Arrange a package structure of golang source code
TEMP: BEGIN: Run groovyserver process only by native command instead of using ServerCLI