Adjust link colors and add visited link color.

Ensure sufficient contrast on the usual page background in
order to be accessible with color deficits. (The visited
link color could still stand out a bit more though.)
Log some messages to help debug per-partner template issue. (#420)
Disable caching on Levels 1 and 2 pages for now.

Despite our inclusion of the vary_on_headers('Host') decorator,
caching seemed implicated in the problem where a Level 1 or 2
key page could get 'stuck' on a particular partner site for
a while. Perhaps only one Level 1 or 2 page per URL path was
being cached despite varying on the Host. (#420)
Added Dan, Greg, and Partners to contributors.
Add missing comma to copy. (#392)
Merge branch 'master' of github.com:newfs/gobotany-app
Accept synonyms during partner site species list import. (#421)
Edit Concord intro text to prevent orphan on desktops and tablets. (#392)
Make the Slider filter appear again.

Dismissing the filter still has a bug. (#425)
Rebuild production JS file.
Remove hardcoded references to newfs S3 bucket, use value from settings if available.
Allow configurable dynamic content image upload path, and set it to the currently used paths.
Merge branch 'upstream'
Add natural key import/export to pertnersite model