Galleries should handle more than travel photos

[rupl]

Curently, a directory is hardcoded into _includes/gallery.html. It assumes the source image is in _img/travel. Different blog sections should have different directories of images.

• [ ] Alter gallery to take a directory as an argument
• [ ] Update gulp processes to handle other directories. This will probably involve reorganizing photos completely, including the existing S3 structure: _site/img/[SIZE]/[DIR]/[SOURCE]
• [ ] Fix any existing blog posts.. I had to dump non-travel images into the _img/travel folder to get publishing quickly.

Here's a list of posts that need to be updated later on:

• 2016-04-17-bustashape-vetenskapsfestivalen-gothenburg-2016
• 2017-01-10-arduino-soil-moisture-sensor
• 2017-01-12-lilypad-arduino-biking-jacket

[rupl]

I could also "solve" this by not caring whether the directory is labeled "travel" or not...