change readme logo link to "http"
The logo link is currently `https`, but the site has no SSL certificate, so Chrome warns me "Your connection is not private" when I click it. This edit changes it to just `http`, so it should (I think) avoid the warning page.
[![Travis Build Status](https://travis-ci.org/googlefonts/fontbakery.svg)](https://travis-ci.org/googlefonts/fontbakery)
[![License: Apache 2.0](https://img.shields.io/badge/License-Apache%202.0-brightgreen.svg)](https://github.com/googlefonts/fontbakery/blob/master/LICENSE.txt)
-# [![Font Bakery](data/logo.png)](https://fontbakery.com)
+# [![Font Bakery](data/logo.png)](http://fontbakery.com)
Font Bakery is a command-line tool for checking the quality of font projects.
