Created by: Hightrack
In order to be more flexible while implementing a design, this pull request create optional classes for grid with half size.
For example: push-sm-2-5 is a push with size 2,5 columns col-sm-4-5 is a column with size 4-5 columns
It is optional and only will be created if the variable $enable-grid-classes-half-size is true.
This will allow to center elements using grid.