Fix travis ci failures

During build, the ci vm download the android tools, and accompanying licenses. As noted in the documentation (http://docs.travis-ci.com/user/languages/android/) without any `licenses` configuration for the `android language`, the vm will only accept the `android-sdk-license-bcbbd656` license. 
I added a regular expression for the `license` argument so it's able to handle future variation of the android sdk license.

Note: the license most likely changes because of Google IO, and the release of new android sdk tools.