Merge pull request #1 from martinghunt/master

Initial functionality: scripts to make a db and run kraken
Add Genbank module for downloading references
added download and clean methods
added download and clean methods
Add option to download extra genomes from genbank
Fix typos
Return array ref, not the array
Fix clean so default is to actually clean up after building
Merge pull request #2 from martinghunt/add_to_kraken_library

Allow adding genbank records to kraken db