Add CORS support

[gmuth]

https://streaming.bose.com returns CORS headers - so should soundcork for web client or BoseApp support:

Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: GET, POST, OPTIONS

• The BoseApps are HTML5 apps using the devices web api as well as the marge api.
• I think the BoseApp queries /info where the response includes the margeURL.
• Then the BoseApp can manage presets by accessing marge directly.
• The BoseApp later uses the /notification endpoint to notify the device about new presets.

(#125)