Copied text from Google Code repository and enabled TravisCI

With this pull request the contents of the [main page on the Google Code site](https://code.google.com/p/rest-assured/) are copied into README file and there's the TravisCI configuration to run all tests on openjdk7, oraclejdk7 and oraclejdk8.

Note: There appears to be a problem with Scalatra on Oracle JDK 8, but it is not related to this pull request.