Merge branches 'master' and 'irwin-taxon_filter' of github.com:broadinstitute/viral-ngs into irwin-taxon_filter
Merge branch 'master' into irwin-taxon_filter
DownloadPackage now uses relative path, defaults to build dir, has post_download_command, and handles .bz2. Removed DownloadScript.
Added tools for picard and samtools.
Include picard and samtools in testtools.
Merge branch 'irwin-taxon_filter' into irwin-tool_enhancements
In tools/__init__.py, set __all__ to automatically contain all tools. Check return from os.system in post_download.
tweak to check
Merge pull request #16 from broadinstitute/irwin-tool_enhancements

Made changes to DownloadPackage and got rid of DownloadScript, handle bz2 compression in DownloadPackage, added post_download_command argument to DownloadPackage, a command that will be executed in the destination directory, created tools for samtools and picard.