Add controls that allow the user to switch to the next and previous song
in cmus, toggle shuffle and repeat. Pause/play is toggled by clicking on
the song title itself.
fixes#5
Font and background colors for warning and critical elements can now be
specified using fg-warning, fg-critical, bg-warning and bg-critical.
Also, optionally, the "urgent" flag will be set towards the i3bar, if
possible.
It is now possible to add a list of theme configurations in the
"default" section called "cycle". These configuration items will be
cycled through module by module. to create "alternate style" effects.
This is *only* possible in the "default" configuration part, but any
module-specific configurations still take precedence.
Also, removed the capability of per-widget themes. That simply
complicates things and probably doesn't really bring any benefits.
Module themes (only!) can now contain state-specific theme information -
for example, the "battery" module has different states for charging and
discharging, and those can have different prefix and postfix
configurations to indicate what is going on.
Individual items in the bar can now be configured with a prefix and a
suffix. It works like this:
* If there is a specific module configuration in the theme
configuration, use that (i.e. { "<modulename>": { "prefix: " a " } })
* Otherwise, if there is a configuration in the "default" section of the
theme, use that
* Otherwise, if the module object itself has a method called like the
required attribute (prefix, suffix), use that
* Otherwise, leave prefix/suffix empty ("")
