Improvements to collection template

Collection header (description and image) can now be configured to
display above or below the products.

Refactor collection—intro section to use semantic css markup so it can
be overridden through SASS in the theme settings (i.e., using
make-##-column() mixing).
Remove adaptive thumbnails setting
Add collection slider
Pull in latest Bootstrapify changes
Merge pull request #201 from luciddesign/artbaygallery

Artbaygallery