Revert "Allow use of required validator with checkbox fields"

This reverts commit e8f30dc41dfebe62529c65b5a2372183cd58a586.
Fail required validator for boolean false.
Merge pull request #167 from DouweM/boolean-checkbox

Have Checkbox editor value be boolean again, and fail required validator for false.
Build
Fix for jQuery 1.9 by trimming template whitespace

Starting in jQuery 1.9 to build a new DOM element with $(str) str needs to
immediately start with a "<", rather than something like "      <".
Merge pull request #172 from elasticsales/master

Fix for jQuery 1.9 by trimming template whitespace
Merge remote-tracking branch 'upstream/master'