Refactor panel

[arunoda]

Refactored the whole codebase and make it easy to add more knobs in the future.
When we are adding a new knob, we simply need to add a story side API with single React component with how to handle it.

Also remove the ACE and simply use an autoexpanding Textarea for that.

[arunoda]

@roonyh Hey look at this codebase.

[arunoda]

@roonyh

I think this has some lint issues. Could you fix them?
And write some tests the Panel and for the main index.js.

Basically we need to test how these reacts when getting events from the channel and firing events to the channel. Use enzyme.

[roonyh]

@arunoda Looks good. A small fix is in #16. Lint fixes and tests for Panel is in #17.

Working on testing functions from main index.js.

[roonyh]

@arunoda had to refactor the code from index.js somewhat to make it easy to test. see the commit 9961394