fix case sensitivity in headers when on an 'Eureka Dongle'

[tmpvar]

the physical chromecast device requires case sensitive headers!

Not sure if we need to keep the other path, let me know. This has been tested with the youtube app, netflix is untested.

Lets track the netflix stuff in #4, and this closes #1

[yocontra]

I'm working on a major change that will allows us to do this cleaner. #2 would allow us to override .start() with a custom ChromeCast specific function when the modelName is 'Eureka Dongle'

I should be done with it in a few and I'll move this code over into that custom class extension

[yocontra]

Inheritance is done - Add any overrides for chromecast to https://github.com/wearefractal/nodecast/blob/master/lib/devices/chromecast.js