offline - use local copies of leaflet.js instead of CDN

use local copies rather than loading from CDN
modularize - move scripts out of index.html

move scripts to their own files out of index.html
cluster markers - add via bower

add Leaflet.markrcluster using bower
cluster markers - cluster nearby markers

cluster nearby markers using default CSS
change missionary-list.js structure to loop through it and enable easier generation by a database
cluster markers - use minified markercluster rather than src