This CL adds typography information to the Sky theme. The values are from the
Material Design spec. I've also applied these values to the stocks app and the
various components.

We're not geting precisely the right typography in some cases because of
https://github.com/domokit/mojo/issues/65.

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1006363004