update README for v0.8.1
version bump to 0.8.0; update README, contributors etc.
PyPI release 0.7.5
update README
update README for 0.7.3
README: update benchmark table
strip build status badge from PyPI README
update README: mention old Python pre 2.6.5 support
update README for version 0.6 + note about tags in HOWTOPUBLISH
update README for version 0.5.1