Wrong position - how to correctly replace default google icons
I tried to replace the original `gmd_play_arrow` icon with the one from this library... Setting the original icon was working perfectly (it's centered), using this library I have to manually adjust the position...

I use the play button in two places, once in a custom view and once in a floating action button:

**Custom View**

```
Drawable d = ContextCompat.getDrawable(getContext(), R.drawable.ic_play_arrow_white_48dp);
```

Replaced with:

```
Drawable d = new IconicsDrawable(context, GoogleMaterial.Icon.gmd_play_arrow).sizeDp(48).paddingDp(2).color(Color.WHITE);
```

**FAB**

```
 fabPlay.setImageResource(R.drawable.ic_play_arrow_white_24dp);
```

Replaced with:

```
 fabPlay.setImageDrawable(new IconicsDrawable(fab.getContext()).icon(GoogleMaterial.Icon.gmd_play_arrow).color(Color.WHITE).sizeDp(24).paddingDp(1));
```

**Result**

On the left you see what it looks like before using iconics, on the right how it looks like afterwards.
The first row shows the custom view, the second row shows a FAB...
As you can see, the size is not the same + the positioning is not correct as well, the icon is off to the left when using iconics

![icons](https://cloud.githubusercontent.com/assets/2437726/13014125/9c4b9666-d1b2-11e5-9edd-cab378ae9240.png)
