Merge pull request #2 from mkischel/master

Implementing an asynchronous client on top of the existing one
Merge pull request #3 from mkischel/master

Follow up on implementation of asynchronous requests
Adding explicit license to the one that was written in pom
[maven-release-plugin] prepare release jgmp-1.4
[maven-release-plugin] prepare for next development iteration
Version bump in docs.