Upgrade handlebars to the 1.1.2 release

The release includes 6 months worth of improvements and bug fixes, some
of them fairly critical.
Merge pull request #88 from sorentwo/upgrade-handlebars

Upgrade handlebars to the 1.1.2 release
Fix dependencies on MultiJson
Release version 0.15
step 1, refactor
change how sprocket registers, we need an engine
Massive cleanup, chomp trailing newline.
remove automatic registration of extensions, temporarily.
cleanup configuration, and add extension configuration