Checkstyle

Added [maven checkstyle](http://checkstyle.sourceforge.net/) support into the build and marked all client class files as final (could split this into a diff patch i guess).

so what is checkstyle?  Its a tool that looks at your code and tries to see if it complies with a project's style.  I have updated the checks so it matches whats in our [docs](http://tachyon-project.org/Startup-Tasks-for-New-Contributors.html).

Currently there are 25274 style errors in the project... (is there any simple file upload site that I can use for PRs?)