Improvement - Readme update

[mkwlf]

consider updating How to get Started section of the Readme.
Update gradle and maven sections with latest version number instead of x.y.z
This is a change of 2 lines on every release...

further consider that compile is deprecated in future releases of the android gradle plugin - maybe add the corresponding implementation maybe as:
For tools com.android.tools.build:gradle:3.0.0 use implementation 'com.xing.api:api-client:2.1.5'

thx in advance