Reponsive sizing improvements

[peacechen]

The responsive sizing algorithm is rather rigid and has proven not to work well for Android. Here are some ideas for anyone interested in submitting a PR to make it more robust.

The first step would be to scale based on DPI and not just container size. That should accommodate a wider range of display resolutions and densities. The next improvement may be to use separate values for iOS vs Android. And finally after that, a lookup table for specific "problem devices" that don't render well with the general formulas.

Previous related issues: #45 #64 #86 #99 #128