Make tiles protocol sensitive and adding missing image

Removed the protocol prefix for the tiles to avoid the "loading mixed active content" warning message on Firefox. Also made the OSM attribution link protocol sensitive.

Additionally added geocoder image which was being loaded without existing.

Note:
Correction the image source in commit message 99ee19d should be https://github.com/k4r573n/leaflet-control-osm-geocoder/blob/master/images/geocoder.png