Browser warning when accessing over HTTPS

[paulmenzel]

Accessing the site securely over https://r-spatial.github.io/sf/, the browser Firefox shows the warnings below.

Loading mixed (insecure) display content “http://pebesma.staff.ifgi.de/RConsortium_Horizontal_Pantone.png” on a secure page
Loading mixed (insecure) display content “https://img.shields.io/badge/license-GPL%20%28%3E=%202%29-brightgreen.svg?style=flat” on a secure page
Loading mixed (insecure) display content “http://img.shields.io/badge/license-GPL%20%28%3E=%202%29-brightgreen.svg?style=flat” on a secure page
Loading mixed (insecure) display content “https://www.r-pkg.org/badges/version/sf” on a secure page
Loading mixed (insecure) display content “http://www.r-pkg.org/badges/version/sf” on a secure page
Loading mixed (insecure) display content “https://cranlogs.r-pkg.org/badges/sf?color=brightgreen” on a secure page
Loading mixed (insecure) display content “http://cranlogs.r-pkg.org/badges/sf?color=brightgreen” on a secure page