[WO-625] Catch exception on socket.oncert

Mozilla's socket is not extensible via Object.preventExtensions(obj)
and throws exceptions when non-prototype function .oncert is added.
The callback function is needed for the other shims.
Merge pull request #133 from whiteout-io/dev/WO-625

[WO-625] Catch exception on socket.oncert
[WO-588] add options to get update notifications in batches
[WO-588] use 25 messages update batches
Update package.json
[WO-588] move maxUpdateSize assignment
Merge pull request #134 from whiteout-io/dev/WO-588

[WO-588] add options to get update notifications in batches
use config defaults
Add socket.io threat model explanation to README
Update README.md
[WO-594] Return own hostname for 'hostname' call from socket.io
Merge pull request #140 from whiteout-io/dev/wo-594

[WO-594] Return own hostname for 'hostname' call from socket.io
WIP: begin browserify build
WIP add unit tests
save package.json to use 4 spaces
Use module.exports instead of exports
Browserify runtime dependencies work
Correct worker paths
Starting app works. Added source maps to build
Remove DOMpurify from main window