Added leaflet-bing.js from https://github.com/shramov/leaflet-plugins/tree/master/layer/tile/Bing.js
Added OS maps via bing and made default if it's enabled - API Key Required
Added OS Maps via bing - Need to add an API key and uncomment section to enable
Merge pull request #2 from m1ari/bing_os

Bing OS Maps Layer from mfa298