Have a go at adding clustering.

This is mostly copy/paste atm
Hack to fix the clustering..

Our staging db is a bit borked… This will hopefully fix it
Tweak map settings, and add open access map icon
Add word boundaries around the DOI regex

Fixes #77
minified leaflet.marketcluster
Undo word boundary fix; instead, use second regex
Updated bug address to oabutton+bugs@gmail.com
Merge pull request #97 from OAButton/9-add-clustering

Add map marker clustering
Merge pull request #98 from OAButton/77-fix-doi-regex

Fix to process DOIs correctly
Merge branch 'develop' into features/mongoengine

Conflicts:
	oabutton/apps/web/templates/web/layout.html