* prevent value from being returned by Context.prototype.lookup if lookupHit is false

* add test for renderability of Array.length via dot notation

* Remove `typeof obj === 'object'` constraint in prop lookup

Allows rendering properties of primitive types that are not objects, such as a string.

* pop lookup needs to use hasOwnProperty for non-objs

* re-add  constraint in prop lookup, but make property lookups for primitives possible through dot notation

* add test to address #589 specifically

* enhance readability of primitiveHasOwnProperty and add comments to explain why it is used in one case but not the other

- Cleaner separation of responsibilities in the code between
  scanning, parsing, compiling, and rendering functions.
- Much faster

This replaces the soft escaping ('&' -> '&') with strict escaping ('&' -> '&'). This new behavior matches that of Ruby and other Mustache implementations.

Other points:
- `dot_notation` currency is changed to use an ASCII character, since the JS interpreters did not appreciate unicode.
- Forward slash is added to escape list c/o OWASP recommendations.