Add ability to set icon and shadow

Modified the tests to check for key existance instead of truthy-ness to
prevent the case of shadow: false causing the shadow param to not be set
Allow sensor to be set to false
Added google api key parameter
Added style parameters for map customization
Remove redundant map operation.
Constantize the pipe escape
Split tests for clarity and fix test naming
Add ability to set multi-points (lat/long) against a single marker type
Updated readme to reflect changes