[ci] Add travis setup, docker-based.
[ci] Add travis setup, docker-based.

Pretty straightforward; need to be enabled in the Travis console tho.

gares/coq,Zimmi48/coq,ejgallego/coq,SkySkimmer/coq,SkySkimmer/coq,JasonGross/coq,Matafou/coq,JasonGross/coq,gares/coq,gares/coq,silene/coq,Zimmi48/coq,coq/coq,coq/coq,ejgallego/coq,ejgallego/coq,silene/coq,Zimmi48/coq,silene/coq,JasonGross/coq,coq/coq,SkySkimmer/coq,gares/coq,gares/coq,Matafou/coq,JasonGross/coq,ejgallego/coq,SkySkimmer/coq,Zimmi48/coq,Matafou/coq,coq/coq