Fix coding style error in starterkit .theme files

When I was integrating Bootstrap with my BLT-based project, BLT's automated coder review tests failed because the default .theme file included with the starterkit (actually all three, but I noticed this with the Sass starterkit) had a whitespace error.

According to the PHP coding standards:

All blocks at the beginning of a PHP file should be separated by a blank line. This includes the /** @file */ block...

This isn't a functional change, but it will make using Bootstrap starterkit themes with tools like BLT (which fail on PHP syntax issues by default) a less grating experience.

I'll attach a patch with the whitespace fix in all three .theme files.

(As an aside: The 'please read the contributing to bootstrap' link at the top of new issues points to a 404 page currently).