more should respect stdin, return, terminal size

[bergey]

• should accept display content on STDIN (and still get keyboard input from terminal)
• should detect terminal size, page by this amount
• should move by line (RETURN) or by page (SPACE)

Are there other features people need to start using more routinely?

[bergey]

Unless someone speaks up to say they're working on this already, I'll put together a PR. Any preference on 1 PR or several?

[ArniDagur]

Thanks for your interest in contributing to the project! I doubt there's anyone working on this already. I'm personally fine with 1 PR if you put them in multiple commits, since these are uncontroversial changes, but @Arcterus's opinion may differ.