Bumps version to 0.5a1.
Increases the unit test connection read timeout again for Travis CI.
Fixes --continue option to be grouped.
Fixes finish time formatting.
Moves readme from Markdown to RST.

This allows proper rendering in PyPI.
Fixes keep alive not working. Implements --no-http-keep-alive.
Adds cache module.
Implements dns caching.
Implements --rotate-dns.