Add support for tags: if_equal and if_not_equal

[adamjohnson]

If you open the backpage of the Design System in hammer right now, it looks like this:

How to reproduce

1. Start hammer: hammer-start
2. Navigate to the backpage template in the design system: http://localhost:2000/wvu-design-system/views/backpage.html

Tags to add support for

if_equal:

<r:if_equal x="{$componentAlign}" y="right">
  <h2><code>if_equal</code> works!</h2>
</r:if_equal>

if_not_equal:

<r:if_not_equal x="{$componentAlign}" y="right">
  <h2><code>if_not_equal</code> works!</h2>
</r:if_not_equal>

Link to tags in CleanSlate repo

cleanslate/app/lib/slate/radius/tags/basic.rb (Github)

These tags are one of three sets of tags heavily used in Design System components.