#54 mouse support

I don't really care about this, however, most terminal emulators (st, [u]xterm, and terminal.app) don't allow you to highlight things in the editor because termbox attempts to do something with the input. The only emulator that doesn't seem to have this issue with iterm2. That being said, I don't want the mouse to jump the cursor but have a separate region called the mouse region.

• mouse 1: selects text
• mouse 2: paste text from clipboard (pbpaste, xclip -out, etc.)
• mouse 3: copy text to clipboard (pbcopy, xclip -in, etc.)

I'm not going to support this through termbox. I have no need for this.