Add travis-ci build for automated testing

Hi guys,

first of all thanks for all your great work. In order to improve quality and testing I would like to suggest an automated Travis CI build. Here is an example of what that would look like:

https://travis-ci.org/tanx/openssl/builds/22838547

The change is quite small but I hope it helps you to get started:

- Add .travis.yml config file
- Add travis badge to README
- Rename README -> README.md to display travis badge in github

If you accept the pull request, a user with admin privileges will have to enable the travis-ci hook under the settings pane of your github repo (it's just one click). Also you may want to change the link of the travis badge in the README.md to point to your repo :)