Update "Install Varnish" section to refer to the server, not client
Update "Install Varnish" section to refer to the server, not client

Client install is already taken care of by "python_requirements.txt".
Closes #162

nuxcode/cartodb,UCL-ShippingGroup/cartodb-1,bloomberg/cartodb,future-analytics/cartodb,nyimbi/cartodb,bloomberg/cartodb,UCL-ShippingGroup/cartodb-1,thorncp/cartodb,codeandtheory/cartodb,splashblot/dronedb,raquel-ucl/cartodb,CartoDB/cartodb,codeandtheory/cartodb,raquel-ucl/cartodb,CartoDB/cartodb,codeandtheory/cartodb,bloomberg/cartodb,CartoDB/cartodb,DigitalCoder/cartodb,CartoDB/cartodb,splashblot/dronedb,thorncp/cartodb,dbirchak/cartodb,splashblot/dronedb,dbirchak/cartodb,future-analytics/cartodb,bloomberg/cartodb,splashblot/dronedb,nuxcode/cartodb,thorncp/cartodb,DigitalCoder/cartodb,UCL-ShippingGroup/cartodb-1,nyimbi/cartodb,nuxcode/cartodb,future-analytics/cartodb,codeandtheory/cartodb,nyimbi/cartodb,future-analytics/cartodb,bloomberg/cartodb,dbirchak/cartodb,UCL-ShippingGroup/cartodb-1,UCL-ShippingGroup/cartodb-1,CartoDB/cartodb,nuxcode/cartodb,dbirchak/cartodb,future-analytics/cartodb,nyimbi/cartodb,dbirchak/cartodb,codeandtheory/cartodb,splashblot/dronedb,thorncp/cartodb,DigitalCoder/cartodb,nyimbi/cartodb,raquel-ucl/cartodb,raquel-ucl/cartodb,nuxcode/cartodb,thorncp/cartodb,raquel-ucl/cartodb,DigitalCoder/cartodb,DigitalCoder/cartodb