Adds a couple utility methods to detect block/block param presence:

* `hasBlock`

  Adds the ability to easily detect if a component was invoked with or
  without a block.

  Example (`hasBlock` will be `false`):

  ```hbs
  {{! templates/application.hbs }}

  {{foo-bar}}

  {{! templates/components/foo-bar.js }}
  {{#if hasBlock}}
    This will not be printed, because no block was provided
  {{/if}}
  ```

  Example (`hasBlock` will be `true`):

  ```hbs
  {{! templates/application.hbs }}

  {{#foo-bar}}
    Hi!
  {{/foo-bar}}

  {{! templates/components/foo-bar.js }}
  {{#if hasBlock}}
    This will be printed because a block was provided
    {{yield}}
  {{/if}}
  ```

* `hasBlockParams`

Adds the ability to easily detect if a component was invoked with block parameter
supplied.

Example (`hasBlockParams` will be `false`):

```hbs
{{! templates/application.hbs }}

{{#foo-bar}}
  Hi!.
{{/foo-bar}}

{{! templates/components/foo-bar.js }}
{{#if hasBlockParams}}
  {{yield this}}
  This will not be printed, because no block was provided
{{/if}}
```

Example (`hasBlockParams` will be `true`):

```hbs
{{! templates/application.hbs }}

{{#foo-bar as |foo|}}
  Hi!
{{/foo-bar}}

{{! templates/components/foo-bar.js }}
{{#if hasBlockParams}}
  {{yield this}}
  This will be printed because a block was provided
{{/if}}
```