Grid and type changes

@tsmith512 

When you have a chance to review this, please let me know what you think. I'm hoping this will be a much smoother transition to Drupal.

## Key changes
* Breakpoints have been adjusted/removed/redefined based on a mobile-first approach to breakpoint design
* Removed em() function - changed $space variable and type measurement unit to pixels
* Changed footer seal to use suggest background-image SVG over inline SVG

## Still to-to
* Fix ```ul``` and ```ol``` ```list-type``` for drupals
* Refine entity bar and search for mobile


Sass provides a convenience function `image-url()` which points directly to your minified images directory as provided by Grunt (on the existing Drupal install; not sure how Gulp is set up here) _or_ when in "Development" mode, your uncompressed images directory where we're putting the original files. So instead you'd write `background-image: image-url(icons/menu.svg)` like I did with the logo and seal stuff. Not a blocker to migrating this in, by any means, but something cool to know about, and we'll switch over to it as we go.