Cleanup

Worked to cleanup CSS and JS so that it would be easier to drop-in to an existing site.

- Moved all compiled css and js to build/ dir
- Moved all compiled css/js to build/ dir
- Put all HTML in template and CSS under single ID selector #att_dialpad
- Removed other IDs from dialpad template
- Use window param in dialpad.js IIFE

Also added one feature:

- Handled letters in keydown. A-Z work to display the correct number on the dialpad.