Changes to annotations for SassDoc 2.0

I added the `multiple : false` key to:

 * `@access`
 * `@content`
 * `@deprecated`
 * `@group`
 * `@output`
 * `@return`
 * `@type`

We need to update:
 * [x] [sassdoc-default-theme#14](https://github.com/SassDoc/sassdoc-theme-default/issues/14)
 * [x] [sassdoc-extras#9](https://github.com/SassDoc/sassdoc-extras/issues/9)

to fix the remaining tests