Add a badge to the readme that links to the latest stable release

[sgarfinkel]

I'm unsure where stable releases are available (they don't seem to be on MavenCentral?) or what version number they are. Adding a badge with a link to the stable release will resolve both problems.

Also, the readme should have some code blocks that provide a minimal Gradle/Maven setup to use crnk. If a badge is added, then that can be used to indicate the version to the user, and the code blocks in the readme won't need to be updated.

[remmeier]

a list of available releases including latest is available from http://www.crnk.io/releases/. but yes, there should be a bit more instructions on the github page. And the badge should be added (again). I tried using the bintray batch a while back, but that point in time it was a bit unstable. Probably worth to try again.

[remmeier]

repositories are documented here: http://www.crnk.io/releases/stable/documentation/#_repository

[remmeier]

added two batches to release version and latest version. And added link to the example application and some basic code snippets. Hope that helps. Input very welcomed.