Converts a list of PCR primer pairs to BED regions

Given a genomic FASTA file and a list of primers,  this will generate a new
FASTA file for the targeted region.  This targeted FASTA file can then be
used for targeted resequencing.

PCR input is expected to be paired FASTA entries with names like:
>primername/1
atatcgtgctacgatc
>primername/2
ttgatcggcatataaa

Tab-delimited input should be:
fwd-primer {tab} rev-primer

Uses http://genome.ucsc.edu/cgi-bin/hgPcr to perform ePCR.

Note: This operates by screen scraping,  so it may break unexpectedly in the
future.

Usage: bedutils fromprimers {opts} -fasta file.fa
       bedutils fromprimers {opts} -tab file.txt
       bedutils fromprimers {opts} fwd_primer rev_primer

Options:
-db         name    DB to use
-perfect    bases   Minimum perfect bases (default: 15)
-good       bases   Minimum good bases (default: 15)
-size       bases   Max product size (default: 4000)
-flip               Flip the reverse primer (default: False)