Equal height utils function for DE pricing grid vertical alignment

This PR addresses MKT-828, https://github.com/optimizely/marketing-website/pull/726, https://github.com/optimizely/marketing-website/pull/738.

Testing instructions are below.  Note that the responsive version of this function does not work for the Pricing page because our grid elements we are targeting are in columns and not rows.
@stewsmith sorry I gave you the wrong function to call.  Also, you won't call window.optly function because it is not defined on the DE page, you have to paste it into the console.  See below for the correct function and here is a demo http://cl.ly/201C430A471Y