Set width of galleria-thumbnails div to 100% conditionally for amount of...

Set the width of galleria-thumbnails div to 100% when sum of thumbnails combined widths exceeds or equals the width of galleria-thumbnails-container div.

Galleria currently sets a fixed pixel amount for the galleria-thumbnails div, and this causes the last thumbnail to wrap and become hidden in cases when the browser is zoomed out significantly. 

The proposed change will make for a more robust display of the thumbnails.