Pass-through mode

[jeremymanning]

Overview
Add an additional button that simply executes the code in the cell instead of generating the chatify UI.

Describe the solution you'd like
It seems like something as simple as this could work:

• Add a button or menu to the UI where the user can select something like "remove UI and run this cell"
• Pressing the button does two things:
  • Removes the %%explain command from the current cell
  • Calls exec(contents) on the cell's contents

Other things to think about

• What's the right interface for this? A button? An additional tab + dropdown menu option? Something else?