fastarious v0.12.0

• #46: Added empty values for Sequence, Quality, SequenceQuality
• #51: Updated the build, cross-compiled with Scala 2.11/2.12
• #52: Dropped spire dependency
• #54: Dropped ncbiHeaders module (hopefully it wasn't used anywhere)
• #25: Changed FASTA-related code to plain old case classes (similarly to FASTQ)
  • Changed parseFasta to Iterator[FASTA] (no Option)
  • Added parseSkipCrap (same as parseFastaDropErrors(skipCrap = true) before)
  • Removed parseFastaDropErrors (replaced with parseFasta)
• Dropped cosas dependency (after #25 and #54 it's not used by anything)