webclient files assume only CommonJS style modules would be present

When using the ShareJS web client files in an app that has separate AMD-style modules, `require` is defined, but `module.exports` is of course not. This results in a situation where ShareJS is doing things like `require('./microevent')`, even though no such module has been defined.

Checking for `require` is not sufficient to determine that CommonJS-style modules are present. It's probably better to check for both `require` and `module`.

The unfortunate temporary workaround for this is having to vendor in "webclient/share.js" and stick a `var require;` at the top of the IIFE.