Remove to_fasta.

to_fasta was meant to add a def line to query sequence, if missing; and
uniquify query sequence ids by appending a number to duplicates.

Older versions of BLAST+ used to crash if query didn't have def line. BLAST+
2.2.25 (SequenceServer's minimum requirement) and higher handle missing def
line in query sequence gracefully. Thus adding def line to the query isn't
needed anymore.

Uniquification of query sequence ids came as a fix for #109. However, recent
changes (SHA: d377d3bc in particular ) obsoletes the fix. BLAST+ internally
numbers the query sequences 1, 2, 3, ..., n. Numbering done by BLAST+ is
available in XML output, on which our HTML result is now based. We use the
numbering done by BLAST+ to created unique HTML ids and thus index doesn't fail
anymore.

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>