Remove Bootcamp when Boot Camp Assist will not

I purchased an iMac from a buddy and recently upgraded to Yosemite so I am learning as I go about Macs. However, I decided I wanted it to be quicker so I purchased an OWC SSD to install as a primary and use the 1TB HDD as a secondary. Before the install I wanted to remove everything and that included the partition for Boot Camp that shows up:

After reading several tutorials and watching a few videos it suggested going to Boot Camp Assistant but every time I go I get this:

Per this question "Boot Camp Assistant: “Your disk could not be restored to a single partition." it says Click "Erase" and select "Mac OS Extended (Journaled)" but this doesn't do anything in Yosemite.

I've tried downloading the latest to a USB drive but that doesn't do anything either.

So my question is in Yosemite how do I remove the partition from Macintosh HD completely?