Update MapView centerDidChange

Ran into infinite loop with centerDidChange panning to center which triggered move. Move set the center and then centerDidChange was triggered and so on.

Now I just check if the map is already at the center. If so, there is no reason to pan.
Merge pull request #57 from edance/patch-1

Update MapView centerDidChange to not trigger infinite loop when panning to current location.
marker popupViewClass
remove popupViewClass from readme
fix for complex views
update leaflet version
bump bower version
version to 0.6.0
new executables
version 0.6
add content property to popupViewClass and look up by string
Add viewDidChange to update zoom and center with passing tests