Fix defaulting to monaco if settings does not contain codeEditor

[knolleary]

We didn't do a complete enough job of defaulting to monaco. If the settings.js file doesn't contain a codeEditor entry, the editor will default to monaco, but the runtime will not have ensured the monaco library was loaded by the editor.

[coveralls]

Coverage increased (+0.004%) to 68.33% when pulling ca20f41 on fix-monaco-default into f760354 on master.