imdb

* Moves IMDb title handling to `module_urltitle.py`, using [OMDb API](http://omdbapi.com) and JSON parsing instead of imdbpy.
* Adds tests for IMDb title handler. 
* Removes `imdbpy` from requirements as it is useless now, same for `module_imdb.py`.
  * `command_imdb` may be (re)implemented in the future.