mavenCentral not required

[felixwiemuth]

It should not be necessary anymore to add mavenCentral() to the repositories in the build scripts as indicated in the Readme. AndroidStudio projects by default include jCenter() which replaces mavenCentral().

[cketti]

jcenter mirrors most of the packages from Maven Central. So right now things work without adding mavenCentral(). But I consider that to be an implementation detail of jcenter, not something that will always be true. I only upload my libraries to Maven Central.

[cketti]

However, I'm open to changing the language in the README to make adding mavenCentral() optional. Suggestions are welcome.

[felixwiemuth]

Yeah, I guess simply changing the text to sth. like "add jCenter() or alternatively mavenCentral() to ... in case the library is not found" saves developers a bit time.