Added the ability to save multiple players and switch between them.

Some white space clean-up (sorry about that)
Moved play methods from plex_library to siriproxy-plex
Added "Add new Plex player" and "Change Plex player to (player)" voice
commands
Players are stored in a hash which gets written to a csv file and
restored upon initialization
BUG:  Saying the IP address of a player is still a bit tricky
Updated readme
Updated config-info.yml (no longer requires plex_client:) PLEASE UPDATE
YOUR "config.yml" ACCORDINGLY