[r1-dev] Allow setting marker options

[francisdb]

Not all the marker options are supported. I'm trying to set the zIndex but that doesn't
seem to be working.

More on the options here:
https://developers.google.com/maps/documentation/javascript/reference#MarkerOptions

A more flexible option would be an options attribute like the map has, but then a better version that does not need a json string. See #80

[nmccready]

This should be completed with this pull
#104