Enables integration with the Travis CI build automation system

Travis CI (https://travis-ci.org/) is a continuous integration build system with hooks into github to allow for automatic build/test status verification for open source projects.  This pull request adds a .travis.yml file that automatically fires off builds and tests across Postgres 9.1, 9.2, and 9.3 on any commit.

Note: README.markdown would need the URLs updated to point to the main project to properly display the build status.