fix panic

change version format

Added unit testing

clean up dbus connection when exiting

 v1.0.0 - Initial release

basic usage notes:

Command line:

```text
𝝺 powerbar --help
Usage of powerbar:
  -charging string
     format string (default "{state} {capacity}% - {usage}W - {H}h {M}m")
  -discharging string
     format string (default "{state} {capacity}% - {usage}W - {H}h {M}m")
  -full string
     format string (default "{state} {capacity}% - {usage}W - {H}h {M}m")
  -waybar
     enable waybar mode
```

Variables:

- `{capacity}`: Percentage of the battery capacity left
- `{H}`, `{M}`: Hour and Minutes left when `state` is discharging, if charging this indicates how long until 100%.
- `{usage}`: How much power is used in watts when `state` is discharging, If charging this indicates how much the battery is receiving.
- `{state}`: The state of the battery. Can be `Charging`, `Discharging`, `Unknown` or `Fully Charged`

An example waybar config:

```json
{
    "layer": "top",
    "position": "top",
    "modules-left": [],
    "modules-center": [],
    "modules-right": [ "custom/powerbar"],

    "custom/powerbar": {
        "return-type": "json",
        "interval": 1,
        "exec": "$HOME/.config/waybar/powerbar -full 'FULL - {usage}W' -charging '{state} {capacity}% - {usage}W - {H}h {M}m' -waybar 2> /dev/null"
    },
}
```

Classes are lower cased, hypened variants of the possible values for `state`

```css
    border-bottom: 0px solid rgba(0, 255, 0, 1);
}

    border-bottom: 2px solid rgb(0, 255, 0);
}

    border-bottom: 2px solid rgb(255, 217, 0);
}
```