Add ES6 Support

[jkap]

This is a somewhat tall order, but I need it for some stuff I'm working on so I'll write it, starting with what I actually need.

• String interpolation (Added support and basic test for template strings #13 and Added support and tests for ES6 Template Strings complexion-js#1)
• ???

[jkap]

I actually just realized that this will require changes in tests-always-included/complexion-js