Updated the runtime to 1.0.12

Hope it's ok to open a PR instead of an Issue, let me know if not.

Handlebars just released a [new version](https://github.com/wycats/handlebars.js/commit/2a073e0993b40b81fbef82f681bb1dd171f2233b), which has some changes that brake [hbsfy](https://npmjs.org/package/hbsfy).

Handlebars@1.0.12 is incompatible with 1.0.11 runtime (handlebars-runtime@1.0.1), which will be the versions picked when installing hbsfy ([package.json](https://github.com/epeli/node-hbsfy/blob/master/package.json#L25))