Add travis CI builds

I added the ability to do travis builds to 0.7.x.  The point of this was two fold...
* Validate that things build and tests work.  
* As a way to document the way to compile things and run the tests.  Assuming that the build status is paid attention to, then this will be self-documenting because for the build to pass this data will need to be updated.   I get back to compiling pallet every so often and always need to look around as to how to do it.

Possible issues
* The settings.xml file that I have put there may not be the exact one wanted.  But it should be close.
* The way things seem to have to be built for pallet on a clean machine is mvn compile and then mvn zi:compile.  If the first step is not done, things don't seem to compile right.  I am not sure whether this is intentional or not.  In any case, depending on your POV you may want to change the .travis.yml file accordingly
* In the travis.yml file I have hardcoded it to use zi version 0.5.5.  When I don't use that version, the errors I get are not as helpful.  But if things compile fine then this is not an issue.  
* Finally, the extra sauce for the README to display the travis status is currently hardcoded to the branch the README is on.  This will cause issues when merging across: no big issue just normal merge conflict crap.  There is probably a better solution but I have not found it yet.

If you take this pull request you will need to set-up your github repo to work with travis.  http://about.travis-ci.org/docs/user/getting-started/ you should only have to follow steps 1 and 2.

There are a decent amount of disclaimers I am making because I don't know your exact configuration for building and some of this work may duplicate of what you all already have working.  However, these disclaimers are all minor and hopefully have helped things along.  What I do love about this change is I can see on the github page the current status of the build.

But feel free to take, ignore, or provide feedback.  All is good.