Fix issues on Polygons with holes

Fixes issue where polygons with holes so that the fill color would not fill into the holes / interior rings

Switch to drawing with ChunkyPNG

Switches drawing library to ChunkyPNG which removes external dependency on imagemagick.

Colors are also now read from geojson as hex color strings instead of rgb / rgba values.

Check for nil properties

If properties exist in GeoJSON but are nil, check to prevent trying to assign convert options with will cause invalid imagemagick command

Bump oj gem to 3.0 release

v0.1.2

Version 0.1.2

Stroke and Fill option from GeoJSON properties

You can now add properties to your GeoJSON features that include the desired stroke and fill options per feature. For more information see details in README

Initial Release

Initial Release supports generating an image from GeoJSON with a focus on drawing MultiPolygon / Polygon data.