Updated documentation to reflect new build process

Updated the readme to reflect the new build script and the extra step
needed for packaging (passing in the 'package' task).

It also looks like the build/test xml output was not listed in the
.gitignore. I've added that but I wasn't quite sure if it's needed as an
artifact downstream.
Merge pull request #260 from hyrmn/updatedocs

Updated readme.markdown to reflect new build process