Use a text area for sentence input.

This by default, it two lines long and wraps the text automatically.

It disables the ability to hit enter though. I think this is OK though.
Add placeholder to input text area.

This makes it so the user sees the placeholder when there isn't any text
in the box.
Add input and submit controls into div well

This makes these elements related visually
Add space to sentence or the last token

Closes #108
Merge branch 'feature/design-pass' into develop