Helpers v4

[toadkicker]

This is the update to bootstrap 4 and modern tooling.

• Drops LESS entirely from the stack in favor of SCSS, therefore drops therubyracer as a dependency as well.
• Introduces Webpack for compiling JS/SASS and removes Grunt
• Introduces Yarn for UI dependency management
• Replaces datepicker with tempusdominus-bootstrap-4 but keeps the JS Api the same
• Updates to Font Awesome 5 as the preferred icon library
• Updates all bootstrap additions to be Bootstrap 4.0 compliant
• Drops support for ruby 1.9 and lower.
• Adds additional helpers
• Integrates with ActionView generators, removing the need for generator scripts

The readme is updated with the latest changes. Cheers!