Removed full width 100% style from switch mixin

- this fixes the issue where grid col widths and the .switch class do not working together (switch width overriding grid widths)
- switch will go to full width either way in testing so far
- see foundation 4 demo for an example of grid/switch css conflict
Merge pull request #2978 from HoldenCreative/master

Removed full width 100% style from switch mixin - fixes conflict with grid and switch css