Merge branch 'release/1.6.0' into develop
Update README

Include link to mailing list.
stream.hls: Encryption key URLs can be relative.

Fixes #186.
cli: Add --player-no-close option.

Resolves #189.
Merge branch 'hotfix/1.6.1' into develop
Convert README.md to rst and add CONTRIBUTING.rst.
plugins.twitch: Only authenticate once.
plugins.twitch: Use the new HLS API.
plugins.justintv/twitch: Add custom stream weights.
cli: Remove rarely used argument shortcut.
plugins.justintv/twitch: Clearer warning on missing rtmpdump.
docs: MPC-HC 1.7 is released.
plugins.livestream: Update for site changes.

Fixes #195.
Update CONTRIBUTING.rst.

Add some info about plugins.
docs: Add info about sideloading plugins.
win32: Add more examples to livestreamerrc.
plugin: Allow plugins to override default_stream_types.
plugins.livestream: Add support for HLS streams.
plugins.ilive: New method of getting the secure token.
plugins.mips: Add missing RTMP parameter.