Improved native blur/focus handling.
Improved native blur/focus handling.

The challenge is to have working together properly with mouse driven
selections.

Fixes #112.

TypesetIO/substance,TypesetIO/substance,michael/substance-1,substance/substance,jacwright/substance,abhaga/substance,andene/substance,jacwright/substance,abhaga/substance,podviaznikov/substance,substance/substance,stencila/substance,andene/substance,michael/substance-1,podviaznikov/substance