Merge branch '2.0.0-wip' into feature/Grid
 * reopened feature/Grid (don't delete feature branches until release moving forward)
added custom column name variables
* resolve #15 github issue: added the ability to declare custom column names.
* moved $column styles to helpers
* converted %columns to `@mixin` to change the way it renders in css
* media query `.push`, and `.pull` classes to now also inherit column styles.
* updated changelog
Merge branch 'feature/Grid' into 2.0.0-wip