Added Travis Continues Integration

* Added Continues Integration of travis.org:
    * it tests against ruby `1.8.7`, `1.9.3` and `2.0.0`
    * it also tests against active-resource `3.0`, `3.1`, `3.2`
    * Login credentails are encrypted (details see https://gist.github.com/apepper/4565343 ).
* Updated `Gemfile` to also work with newer gem version.
* Added Travis Batch to Readme ( [![Build Status](https://travis-ci.org/infopark/crm_connector.png?branch=master)](https://travis-ci.org/infopark/crm_connector) )
* Improved Readme to state, that it also supports ruby 2.0.0

(Almost) green Travis: https://travis-ci.org/apepper/crm_connector/builds/5651505
(Almost) green Cruise: http://cruise.infopark:3000/project/show_build/15106