Fix jekyll build error on FSF site

We had a few errant problems on the site that I was able to debug by running jekyll locally.  We had "<br> </br>" in a few places as well as extra underscore characters.

I apologize for the sweeping cleanup that I did on testimonials/index.md, but I was chasing down a series of errors and I decided to standardize the page in an effort to get to the solution faster (each fix yield new errors, so standardizing the page meant cleaning the errors up in the second pass versus fifth or sixth pass).