Update Docker installation documentation
Update Docker installation documentation

This doc is geared around Ubuntu 14.04, and the Docker docs now recommend installing Docker via wget.
briehl/narrative,jmchandonia/narrative,briehl/narrative,msneddon/narrative,kbase/narrative,kbase/narrative,jmchandonia/narrative,jmchandonia/narrative,msneddon/narrative,jmchandonia/narrative,jmchandonia/narrative,mlhenderson/narrative,psnovichkov/narrative,jmchandonia/narrative,briehl/narrative,briehl/narrative,psnovichkov/narrative,kbase/narrative,jmchandonia/narrative,psnovichkov/narrative,pranjan77/narrative,mlhenderson/narrative,mlhenderson/narrative,briehl/narrative,kbase/narrative,pranjan77/narrative,mlhenderson/narrative,msneddon/narrative,psnovichkov/narrative,msneddon/narrative,msneddon/narrative,briehl/narrative,pranjan77/narrative,psnovichkov/narrative,pranjan77/narrative,psnovichkov/narrative,pranjan77/narrative,mlhenderson/narrative,kbase/narrative,pranjan77/narrative,psnovichkov/narrative,pranjan77/narrative,msneddon/narrative,msneddon/narrative,mlhenderson/narrative,kbase/narrative,briehl/narrative