Shows and controls alsa volume with a progressbar.

Dependencies:

- alsa-utils (of course)

Plus tooltips, notifications, and color changes at mute/unmute switch.

	myvolumebar = lain.widgets.alsabar()

* Left click: Launch `alsamixer` in your `terminal`.
* Right click: Mute/unmute.
* Scroll wheel: Increase/decrase volume.

The function takes a table as optional argument, which can contain:

Variable | Meaning | Type | Default
--- | --- | --- | ---
`width` | Bar width | int | 63
`height` | Bar height | int | 1
`ticks` | Set bar ticks on | boolean | true
`ticks_size` | Ticks size | int | 7
`vertical` | Set the bar vertical | boolean | false
`channel` | Mixer channel | string | "Master" 
`step` | Step at which volume is increased/decreased | string | "5%"
`colors` | Bar colors | table | see **colors**
`notifications` | Notifications settings | table | see **notifications**

### colors

Variable | Meaning | Type | Default
--- | --- | --- | ---
`background` | Bar backgrund color | string | `beautiful.bg_normal`
`mute` | Bar mute color | string | "#EB8F8F"
`unmute` | Bar unmute color | string | "#A4CE8A"

### notifications

Variable | Meaning | Type | Default
--- | --- | --- | ---
`font` | Notifications font | string | The one defined in `beautiful.font`
`font_size` | Notifications font size | string | "11"
`bar_size` | Wibox height | int | 18

It's **crucial** to set `notifications.bar_size` to your `mywibox[s]` height,
**if** you have set it different than default (18). 

`lain.widgets.alsabar` outputs the following table:

Variable | Type
--- | ---
`widget` | `awful.widget.progressbar`
`channel` | string
`step` | string
`notify` | function

Finally, you can control the widget with the following key bindings:

        -- Volume control
        awful.key({ altkey }, "Up",
        function ()
            awful.util.spawn("amixer sset " .. volume.channel .. " " .. volume.step .. "+")
            volume.notify()
        end),
        awful.key({ altkey }, "Down",
        function ()
            awful.util.spawn("amixer sset " .. volume.channel .. " " .. volume.step .. "-")
            volume.notify()
        end),
        awful.key({ altkey }, "m",
        function ()
            awful.util.spawn("amixer set Master playback toggle")
            volume.notify()
        end),
        awful.key({ altkey, "Control" }, "m", 
        function ()
            awful.util.spawn("amixer set Master playback 100%", false )
            volume.notify()
        end),

where `altkey = "Mod1"`.