Add Windows unset shell variables instructions
Add Windows unset shell variables instructions

Instructions on unsetting docker-machine shell variable settings covered Mac/Linux only. Adding instructions for Windows too.
JimGalasyn/docker.github.io,thaJeztah/docker.github.io,anweiss/docker.github.io,johnstep/docker.github.io,thaJeztah/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io,londoncalling/docker.github.io,anweiss/docker.github.io,anweiss/docker.github.io,thaJeztah/docker.github.io,JimGalasyn/docker.github.io,anweiss/docker.github.io,JimGalasyn/docker.github.io,johnstep/docker.github.io,docker/docker.github.io,johnstep/docker.github.io,anweiss/docker.github.io,londoncalling/docker.github.io,JimGalasyn/docker.github.io,londoncalling/docker.github.io,londoncalling/docker.github.io,docker/docker.github.io,docker/docker.github.io,londoncalling/docker.github.io,JimGalasyn/docker.github.io,johnstep/docker.github.io,johnstep/docker.github.io,docker/docker.github.io