add browser support to PBF parser?

Note: this is not an actual request to merge, just as a reference

I did a quick and dirty test for using pbfParser in the browser (not caring about Node.js).
Example: http://nrenner.github.io/osm-read/

I'm thinking about discontinuing [osm-pbf.js](https://github.com/nrenner/osm-pbf.js) and switching to osm-read because it's based on ProtoBuf.js and already supports reading some metadata, but:

1. While my test is using shims and replacements for the node-specific parts, I would rather factor these out and have a neutral core. Browser support could then be added here or as a separate project. What do you think?

2. Do you care about the GPL license and it's strong copyleft? I would prefer a permissive license like MIT,  2-clause BSD or Apache License (used by ProtoBuf.js) that doesn't require other projects using the library to also use GPL.