(feat) Allow Chromecast to be called externally

[MGSousa]

At this moment, I'm using this awesome tool as a Backend on an app that I'm developing, which allows custom control of Chromecast devices from a mobile phone.

With that, I made several, yet simple changes:

• to allow go-chromecast to be called externally by other libraries, CLI, tools, mobile apps, etc.
• removed some deprecations, minor code improvements