v6.0.1

Major redesign

1. rewrites all logic to use DataView objects (available in node and the browser) instead of node buffers.
2. Avoid all node specific APIs in the library and its dependencies, this includes changing to use but-unzip for unzipping stuff.
3. no more poly filling for older browsers, this means we've gone from 234K MINIFIED to 226K UNMINIFIED (97k minified).
4. Adds new API to pass an object containing shp and optional dbf, prj and cpg properties, allowing you to easily shapefile where the pieces were given to you individually, (it's the same, function, just accepts an object now).
5. updates to the readme.