Add support for almond.js [Fixes #81]

It would seem that because almond.js does not make any requests to external files (due to it being a library for concatenated AMD modules), we can check whether the AMD implementation has the `require.load` function - which is used to load external files into the DOM.

So, ideally, this should fix issue #81. I've set the module name to `Bugsnag` to match the name of the global variable Bugsnag uses when no module loading library is used.

Feedback?