Add styles to enforce wireframe mode when applied
Adjustments to typography:

- ensure base font size is actually applied to the body
- bump up base font-size from 13px to 15px to improve legibility and
  bring closer to browser default (16px)
- adjust line-height and h1..6 measurements accordingly
- add lorem ipsum to typography sample
Overhaul .input-container and .btn:

- use line-height, not top/bottom padding, for vertical dimension
- refactor inner dimensions (line-height & padding) into a new
  .btn-sizing helper, applied in both input-container and btn
- input-container now sizes the same with and without a button inside
  (obviously a button expands the right side though)
- try to fit the button/input-container icon inside the space that would
  be the element's padding - for large and up there is no change in
  width with/without icon