When removing a DynamicMapLayer that is outside the min/max zoom levels, the _currentImage is null.  Added a check to prevent a accessing a null value.
Merge pull request #195 from johnwebbcole/master

When removing a DynamicMapLayer that is outside the min/max zoom levels,...
Update esri-leaflet.js

Added check that there is content in "cells" array, otherwise loading events are fired without corresponding load events.
added Tiled Map Service sample

nipped someone in the forum:

http://forums.arcgis.com/threads/100962-esriLeaflet-with-my-own-tiled-map-service
Merge pull request #196 from Greigrm/patch-1

Update esri-leaflet.js
Merge pull request #197 from jgravois/master

added Tiled Map Service sample