Package dependencies security: upgrade Handlebars to 4.0.0

[zachelrath]

There is an open CVE that affects dmc because of its dependency on Handlebars 2.0.0. The recommended fix is to upgrade to 4.x

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-8861

[zachelrath]

Resolved by #45