Adding ability to convert reference FASTA files for nucleotide sequences.
Merge pull request #79 from bigdatagenomics/fasta

Adding ability to convert reference FASTA files for nucleotide sequences
Added the "tags" command, and parsing for BAM attributes.

Added code (in Attribute and AttributeUtils) to parse attributes -- the optional fields at the end of a SAM record -- from the string which is stored in the ADAMRecord. Updated the adam-cli project with a command, 'tags', that reads an ADAMRecord set and prints the total set of tags found in the set, along with the number of times each tag appears.