Use module name when __sourceUrl undefined

When an error occurs during __eval, fall back to module name value when
sourceUrl is undefined.
Merge pull request #131 from jgable/moduleNameOnError

Use module name when __sourceUrl undefined
starting to get source maps in Firefox
Merge pull request #133 from guybedford/master

starting to get source maps in Firefox
remove sourceURL checks
fixes #134
spec update
circular references support