Combine tagsUrlSafe and tagsCollection into one property

[jarodtaylor]

This commit combines the tagsCollection and tagsUrlSafe properties into one property, named by the plugin option handle, or "tags" by default.

The tags property will now return an array containing an object with a name and slug property that can be used like so:

{{#each tags as |tag| }}
  <a href="{{tag.slug}}">{{tag.name}}</a>
{{/each}}

As discussed in #34, this would be a breaking change, that would be held onto until the next major release.

[hswolff]

This looks great! Gonna merge and bump version number.

[hswolff]

Published as 2.0.0