Unsafe Global Name topojson

[ZheyangSong]

Because of HTML5's standards, every DOM element with unique id will be stored on window object with the id as the key and DOM element as the value. Thus, when there is an element with id="topojson", the window.topojson is contaminated before registering methods from topojson.js. The transform method has a name conflict with the SVG read-only attribute transform, eg. when <svg id='topojson'></svg> presents, the library's initialization will fail. You'd probably want to find another name for the method to avoid the collision... :)