All helper calls will have access to `options.name` which is the first id value of the mustache operation.
As part of this the helperMissing call has been simplified to remove the indexed name in order to optimize the call. This is a breaking change.
Fixes#634
The idea is that the environment wraps up the mutable stuff in
Handlebars (like the helpers) and that you could theoretically create a
new one at any time and pass it in to Handlebars.template.
Every test makes a new environment and uses it in template compilation.
Jesse Ezell
kpdecker
Yehuda Katz