Fix Sphinx formatting error in writing_benchmarks.rst
Open preview in webbrowser
Fix #42: Try random ports until an available one is found.
Handle missing func better
Fix `asv run existing`
Be more explicit about how `asv machine` works in the docs so it's
easier to follow along.
Fix #50: Allow sorting of lists with None and string intermixed.
Blacklist virtualenv 1.11.0.  Fix #52.