Minimal support for browser-loaded anonymous modules

With these small changes almond.js can provide minimal support for browser-loaded anonymous modules.

Anonymous modules (e.g. lodash.js, when.js) expect to be named through path mapping.  In this case, a name *may* be determined at run-time *if* we're in the browser and the script is being synchronously loaded via the &lt;script&gt; tag.  In this case, we're guaranteed that the currently executing script is the *last* one in the current DOM -- in fact, it should be the last DOM element (ref http://ejohn.org/blog/degrading-script-tags/ )