Updated avocado to move to org.bdgenomics, and to move to ADAM 0.8.1-SNAPSHOT

This pull request makes the following changes:

* Moves all packages to org.bdgenomics
* Upgrades ADAM to 0.8.1-SNAPSHOT. This requires us to do s/Adam/ADAM/g, as well as s/edu.berkeley.cs.amplab.adam/org.bdgenomics.adam/g.
* Runs [scalariform](https://github.com/mdr/scalariform) on all files.
* Adds changelog (CHANGES.md, updated via scripts/changelog.sh)
* Adds CONTRIBUTING.md file.