* Add bowtie2@2.3.0, fix dependencies and sbangs
Add support for bowtie2@2.3.0
- digest
- a patch for 2.3.0 that parallels the existing package. Truth be
told it builds (for me) without this, but I'm assuming that they're
there for a reason...).
- tune up dependencies
- need tbb
- don't need readline or zlib
Several things were installed with sbang's that use `/usr/bin/env` to
fine perl or python. Fix the dependency and clean up the sbang lines.
* Fix python exe name, avoid path banging
I'd cut and pasted the python bit from the perl bit and missed one
reference to perl.
While I'm there, use the cleaner `spec['perl'].command` instead of
banging together the path from its bits.
* Fix up the "when" constraints on the dependencies
Get the edge cases right.
- 2.2.5 doesn't need tbb, 2.3.[01] do.
- 2.3.1 needs readline and zlib.
