Show photos on crop page

As a side effect of this, we moved a bunch of chunks of the crops page
out into partials.  We also moved photo thumbnails (as formerly seen on
the plantings page) into a partial, and then used it to display photos
on the crops page as well.
added Marty to CONTRIBUTORS.md
Merge pull request #263 from Skud/crop_photos

Crop photos
fixed(?) firefox bug with email address in location field
added RSS feed for seeds
added metadata to plantings RSS
removed author fields from RSS
Review and cleanup of JSON API

Removed JSON from classes that shouldn't have it.
(PT: https://www.pivotaltracker.com/story/show/54570954)

Also found a couple of controllers with broken authorization (i.e. not
checking CanCan). Incidentally, this also fixes the comment form bug at
https://www.pivotaltracker.com/story/show/54328716.
Merge pull request #266 from Skud/seeds-rss

Seeds rss
Merge pull request #265 from Skud/profile-email

fixed(?) firefox bug with email address in location field
Merge pull request #267 from Skud/api-review

Review and cleanup of JSON API
added recent scope for crops
roughed in the framework for new homepage design
roughly got crops/plantings working for new homepage
Added blog and email icons

Both are free/unrestricted use:

Blog icon from http://theblogicon.com/
Email icon from http://commons.wikimedia.org/wiki/File:Email_social_icon.svg
Added "keep in touch" links to sidebar
Sidebar: keep in touch, and open stuff
style tweaking
Added a popover for planting images too.
refactored 'interesting plantings'