Multi-segment CDS tests for N-ends code (ambg{5,3}{c,f,s} alerts).

Two fasta files:
1. entoy100a.nends.fa:
   Sequence names are somewhat descriptive.
   Some of these examples were based on FP-175. See the description of
   that JIRA ticket.

> esl-seqstat -a $VADRSCRIPTSDIR/testfiles/entoy100a.nends.fa
= ENTOY100A-pass                 100 
= ENTOY100A/one-4Ns-start-11-14      100 
= ENTOY100A-one-4Ns-end-28-31      100 
= ENTOY100A-one-4Ns-start-4Ns-end-11-14,28-31      100 
= ENTOY100A-one-second-posn-N-12      100 
= ENTOY100A-one-second-to-final-posn-N-30      100 
= ENTOY100A-one-second-to-final-posn-R-30-pass      100 
= ENTOY100A-one-first-position-N-11      100 
= ENTOY100A-one-final-position-N      100 
= ENTOY100A-one-12Ns-start       100 
= ENTOY100A/one-cds-two-codons-len6-26-31      100 
= ENTOY100A/one-cds-only-stop-len5-27-31      100 
= ENTOY100A/one-cds-only-stop-len4-28-31      100 
= ENTOY100A/one-cds-only-stop-len3-29-31      100 

2. entoy100a-rev.nends.fa:
   Same as 1 but reverse complemented for use with entoy100a-rev model
   which is identical to entoy100a but is reverse complemented. 
   This seq file was created with this set of commads:

   $ esl-seqstat -a entoy100a.nends.fa | grep ^= | awk '{ print $2 }' | awk '{ printf("%s-rev 100 1 %s\n", $1, $1); }' | esl-sfetch -Cf entoy100a.nends.fa - > entoy100a-rev.nends.fa

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See $VADRSCRIPTSDIR/testfiles/entoy100a.genematchcds.minfo and
$VADRSCRIPTSDIR/testfiles/entoy100a-rev.genematchcds.minfo and for
coordinates of each feature.

TODO: 
- add more complicated examples from cds two and three in entoy100a
- add examples on reverse strand in entoy100a.rev, possibly mirror
  images of the other examples, to test reverse strand.

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