prank: New formula

- Fixes #44
- Version 121218
- HEAD available

PRANK is a probabilistic multiple alignment program for DNA, codon and
amino-acid sequences.
paml: 4.7 as --devel

- Install examples, too
- Caveat about doc, examples, dat and ctl files.
Bowtie2 2.0.5
abyss: build dependencies for --HEAD

Building --HEAD requires autoconf, automake and multimarkdown.

Fixes #52