Travis CI support

This pull request add support continuous integration building of sysdig on [Travis CI](https://travis-ci.org/). In order to enable this feature, the [Github webhook](http://docs.travis-ci.com/user/getting-started/) need to be configured. Also, this pull request contains a fix for the Clang build so it can actually pass.

Signed-off-by: Christian Babeux <christian.babeux@0x80.ca>