isEmpty should check for empty objects

I understand this [part](http://handlebarsjs.com/#conditionals) of the documentation

> when used with an empty ({}) context, will result in:

as if you have an empty object, the value will be considered "falsy".
Handlebars.Utils.isEmpty(context) has no check for empty objects, so did I just understand the documentation wrong?

Anyhow, I would like to have a check on empty objects, thus the pull request. :)