How to hide CI from being detected

I just tried the Chrome extension BuiltWith TechnologyProfiler. Just a short click on the extension and it tries to detect and show all technologies used by the website you have currently open in your browser tab.

I tried it with some of my websites and it always detected the use of Codeigniter (see Screenshot). 
I already changed the name of Session_Cookie but that didn't help. 

Do you know how they detect CI and how do disable the detection?

Thanks in advance
Markus