Change dead google code images url to new github url

[pirate]

Images urls pointing to their old library no longer work, and have to be changed, e.g.:

http://google-maps-utility-library-v3.googlecode.com/svn/trunk/markerclustererplus/images/m2.png

to
https://raw.githubusercontent.com/googlemaps/v3-utility-library/master/markerclustererplus/images/m2.png

[mikesaidani]

Looks good to me :)

Thanks !

[wedneyyuri]

@mikesaidani Do you have plans for the next release?

[mikesaidani]

@wedneyyuri I just published the new version to NPM :)