Use Gin in the server instead of Gorilla

[jawher]

Gorilla is a very thin api on top of net/http, and we are still required to do a lot of plumbing to implement the server endpoint.

I propose we move to Gin: https://github.com/gin-gonic/gin
Which would greatly simplify the server code and offer us better productivity.

[haklop]

+1 !

[julienvey]

Whatever makes the job :)