Updating project and dependencies

Hi,

First of all: Thanks for a great library we've been having a lot of success using. Great stuff!

This pull requests aims to bring the project slightly more up to date, and contains the following changes:
- Update project.clj to Leiningen 2
- Update POI version to 3.9
- Add profiles for Clojure version 1.3, 1.4 and 1.5-RC1
- Add .travis.yml to get support for running tests on Travis CI

All tests pass (see https://travis-ci.org/ragnard/docjure) after these changes.

Is this project actively maintained and will you have time to consider any patches/pull requests?

We would also very much appreciate a proper release (ie. not a SNAPSHOT) to clojars.

Please let me know if there is anything I can do to help. I also have some code for better supporting encrypted workbooks and would be happy to submit more pull requests.

Best regards,

Ragnar