Improved the single episode play #70

It now supports:

play s1e2 name  // season first, name last.
play e2s1 name  // episode first, name last.
play e2 name    // episode first (no season), name last.
play name s1e2  // name first, episode last.
play name e2s1  // name first, season last.
play name e2    // name first, no season provided => default to season 0.

play name       // only name (plays next episode) should still work.

... Although, I can't say the code is well written. I will have to spend
a bit of extra time to make it less crappy.