[Enhancement] Center align layers with "min width" padding
Hi! I have a huge library with buttons, and all of them have "min width" specifications. In this case, the paddings are 15; 24; 17; 24 and width >=100. When I use a short title for my button, such as "Add", the plugin automatically fits the width to 100 px (it's super cool!), but the text field doesn't seem to be aligned to the centre. 
![alignment](https://user-images.githubusercontent.com/36654817/36408376-c94d77e6-1626-11e8-968b-f94c5b7ec10a.gif)
