Add "browser" property to package.json.
Add "browser" property to package.json.

This indicates that the "fs", "path", and "crypto" packages should be empty objects in a browser context, since they aren't actually required in that case even though require statements are present. This prevents webpack, etc. from trying to include them. Addresses #83.

mdaines/viz.js,mdaines/viz.js,mdaines/viz.js,mdaines/viz.js