Adding examples for passing assemble.options to custom helpers and bumping version.

This PR adds some examples and bumps the version.

Any `assemble.options` are passed to custom helpers when the helper defines the `register` method.

Set up the assemble build in the `Gruntfile.js`:
```js
assemble: {
  options: {
    flatten: true,
    assets: 'test/actual/assets'
  },
  custom_helpers: {
    options: {
      helpers: ['test/lib/**/*.js'],
      version: '<%= pkg.version %>'
    },
    files: {
      'test/actual/custom_helpers.html': ['test/custom_helpers/custom_helpers.hbs']
    }
  }
}
```

In the `helpers` folder I have a file that registers a custom `opt` helper to get a property from the `assemble.options` object and return it:
```js
module.exports.register = register = function(Handlebars, options) {

  Handlebars.registerHelper('opt', function(key) {
    return options[key] || '';
  });

};
```
This helper can now be used in a Handlebars template like this:
<div>Version: {{opt 'version'}}</div>

This code is all available in this PR