Added indexes for easier playing of new episodes

Issuing "list" will display indexes besides names, issuing "play 1" will
play the show at that index, makes it easier to play long named shows
that don't autocomplete well.

Crude implementation, still has following problems:

- Limited to new episodes of currently watched shows since episode number
is not parsed

- Shows need to have been listed in current instance for this to take effect. e.g. "play 1" will return episode not found if "list" is not called first.

- Formating is slightly unaligned as a result of adding the number.
Merge pull request #74 from IDex/master

fixes #73
Merge branch 'master' of https://github.com/z411/wmal-python into listindex
Indexes are properly formatted
Allows index be used to play any episode

Eg. "play 5 5" plays the fifth episode of fifth show on last viewed list.