commandline client improvements

Output pretty JSON instead of pprint for show_current_config.

Add the show_current_activity and start_activity commands.

show_current_activity dumps the JSON block for the current activity from
the config.

start_activity takes a positional param of either the activity id or
activity label and starts that activity.
add sync command

Add sync command to client and commandline app.

The sync command is like the 'sync now' command in the mobile app, it
forces a sync of the hub with the changes on the harmony web service.

Tested to work properly.
update README.md for github

Add examples of new commands.