REL: Update pavement.py.
REL: Update pavement.py.

Point release notes to doc/release/1.8.0-notes.rst
Set LOG_START to 'v1.6.0'
Set LOG_END to 'maintenance/1.8.x'
Set DEFAULT_PYTHON to '2.7'
Remove Python 2.5 and 3.1 builds.

NextThought/pypy-numpy,NextThought/pypy-numpy,NextThought/pypy-numpy,NextThought/pypy-numpy