[feature] Add support for GeoJSON

[totallynotvaishnav]

We have to add support for loading map data using GeoJSON in the geographic map feature. The steps involved are:

• Accept a new parameter GeoDataParam when creating the NetJSONGraph instance which points to the GeoJSON data.
• Create a new function to parse this link and load GeoJSON data in netjsongraph.utils.js.
• Add a new property to NetJSONGraph called GeoData.
• Render the GeoData using geoJSON method of leaflet library.