Remove "composer self-update" to speed-up tests
Remove "composer self-update" to speed-up tests

re: https://github.com/pantheon-systems/cli/pull/177#issuecomment-77897327
pantheon-systems/cli,dustinleblanc/terminus,labboy0276/cli,pantheon-systems/cli,hugovk/cli,labboy0276/cli,mkudenko/cli,dustinleblanc/terminus,rvtraveller/terminus,rvtraveller/terminus,devekko/cli,mkudenko/cli,rvtraveller/terminus,hugovk/cli,dustinleblanc/terminus,reynoldsalec/cli,Blueprint-Marketing/cli,pantheon-systems/cli,devekko/cli,reynoldsalec/cli,Blueprint-Marketing/cli,devekko/cli,mkudenko/cli,Blueprint-Marketing/cli,labboy0276/cli,reynoldsalec/cli,hugovk/cli