Refactor, add tests.

* Adds mocha and expect.js for tests
* Refactors code heavily, mostly on the osm2geojson side
* Exports functions as module.exports for node & browserify
* Adds package.json for browserify
Improve readme, remove license.md
Restrict multipolygon to actual polygons
Merge branch 'pr/2'

Conflicts:
	README.md
	osm2geo.js
Removed osm2geo