.travis.yml: bump required go to 1.4
.travis.yml: bump required go to 1.4

This is because of a butterfly effect of Google's API client changes
that broke building on <Go1.4. Once I've cherry picked out parts
of their API client, I'll drop it back to 1.2.

fgrosse/drive,dzhsurf/drive,fgrosse/drive,odeke-em/drive,wadtech/drive,OldDragon2A/drive,cacack/drive,pefoley2/drive,PseudoAj/drive,FreedomBen/drive,js-ojus/drive,aeppert/drive,Laeeth/drive,brianjking/drive,aeppert/drive,PseudoAj/drive,sselph/drive,tom-saunders/drive,gdm85/drive,hatchling/drive,sjfloat/drive,shaunstanislaus/drive,miguelinux/drive,cacack/drive,js-ojus/drive,odeke-em/drive,hidehide55/drive,shaunstanislaus/drive,FreedomBen/drive,OldDragon2A/drive,Dedsec01/drive,sselph/drive,sjfloat/drive,hidehide55/drive,stffrdhrn/drive,gccpacman/drive,Laeeth/drive,wadtech/drive,mralexgray/drive,Dedsec01/drive,pefoley2/drive,Qbitz/drive,gdm85/drive,orinocoz/drive,mralexgray/drive,miguelinux/drive,brianjking/drive,tom-saunders/drive,Qbitz/drive,hatchling/drive,gccpacman/drive,dzhsurf/drive,orinocoz/drive,stffrdhrn/drive