biology/py-bx-python: Update to 0.8.1

Additional port changes:

• Changed to DISTVERSION.
• Added USE_PYTHON=cython.
• Added stripping.
• Updated maintainer e-mail.

Reported compiler warnings to the upstream.

Reported by: portscout
Approved by: tcberner (mentor)
Differential Revision: https://reviews.freebsd.org/D14283