Features/pomodoro cmus

Few enhancements for `pomodoro` and `cmus` plugin.

 1. `pomodoro`:
     * Right click now resets timer (stops it)
     * `format` could be configured now 
     * Output _'progress'_: (1/4, 2/4, 3/4 etc)

2. `cmus`:
    * Adequate message when no `cmus` is running
    * Attempt to extract title/artist from filename/stream