Updated to leafletjs from version 0.3.0 to version 0.5.1 (latest stable).

Notable changes in leaflet:
- Adds better support for touch devices.
- Adds keyboard control of map (+/- to zoom, arrows to move)
- See https://github.com/Leaflet/Leaflet/blob/master/CHANGELOG.md
  for full changelog.
Merge pull request #20 from crussell52/master

Updated Leaflet API from version 0.3.0 to version 0.5.1