Sourcemap support

[wied03]

• [x] Working in Chrome
• [x] See if recent refactoring has caused problems here, need to add more rollups first
• [x] Note that rolled up assets don't have source maps
• [x] Sources/file populated to mirror the same file tree
• [x] See https://github.com/opal/opal-rspec/issues/36 - might want to remove the sourceMapResults code and add stacktrace-js to the project, call StackTrace.get() inside KarmaFormatter with a filter that excludes opal and opal-rspec library files, then use that for the failed example result
• [ ] Rubymine can see that there are original script files and hides the compiled JS, but does not stop on breakpoints - Jetbrains ticket
  • Might want to take a known case w/ Rubymine and see what's different. Standard source maps don't work in Karma w/ coffeescript so probably no basis for comparison.
  • Sent them a cleaner way to reproduce the problem
• [x] Allow disabling source maps, you can do this by not including the middleware, but test that and make sure it doesn't blow up

[wied03]

Will address rubymine ticket later