Scale labels based on distance

[pjcozzi]

CC #93 and #1074

[pjcozzi]

Perhaps outside the scope of this issue, but we can consider signed distance fields (perhaps gl-sprite-text) to improve visual quality here.

[pjcozzi]

For signed distance fields, this is a useful read: http://www.essentialmath.com/blog/?p=111

[pjcozzi]

Also see http://wdobbie.com/post/gpu-text-rendering-with-vector-textures/

[tokyovigilante]

There's a Metal implementation of SDF here - http://metalbyexample.com/rendering-text-in-metal-with-signed-distance-fields/

[pjcozzi]

Cool, thanks @tokyovigilante!

[bagnell]

For resources on different font rendering methods, including SDF, see - http://aras-p.info/blog/2017/02/15/Font-Rendering-is-Getting-Interesting/