Add Explainations Somewhere to the Current GFI-Bot LOGO

[hehao98]

The current GFI-Bot logo is designed by Haonan Su. It currently looks good, but, in my opinion, its meaning is not obvious to others interested in our project. Maybe it is better to add some explanations in README.md to explain the rationale of LOGO design.

[minghuizhou]

so cute, but don't know what it is, :-).

[hehao98]

Another option is to design a new logo that is self-explanatory (or we explain it somewhere in the repo and in the website) :-)