travis-ci: Test all databases in a single run, rather than use flaky Travis matrix.
travis-ci: Test all databases in a single run, rather than use flaky Travis matrix.

Previously Travis CI would run many instances as the permutation of all
Ruby interpreters and all databases. Now it only runs one instance per Ruby
interpreter.

The problem is that Travis CI frequently fails with "The virtual machine
is being powered down" if it's running too many instances. The solution is
to stop using Travis' "env" matrix to spawn instances per database and
instead use the new `rake spec:db:all` task.

kerrizor/calagator,Villag/dentonator,CorainChicago/ActivateHub,CorainChicago/ActivateHub,CorainChicago/ActivateHub,kerrizor/calagator,L2-D2/calagator,bencornelis/calagator,iamBalaji/Calagator,cp/calagator-1,shawnacscott/calagator,bencornelis/calagator,reidab/calagator,iamBalaji/Calagator,nblackburn87/calagator,CorainChicago/ActivateHub,reidab/calagator,jmcduffie32/calagator,iamBalaji/Calagator,oktober/calagator,Eugator-Wranglers/calagator,VolunteerOdyssey/calagator,shawnacscott/calagator,nblackburn87/calagator,bencornelis/calagator,L2-D2/calagator,VolunteerOdyssey/calagator,kerrizor/calagator,oktober/calagator,bencornelis/calagator,Villag/dentonator,VolunteerOdyssey/calagator,cp/calagator-1,eeeeeean/windchimes,reidab/calagator,dudleysr/calagator-workspace,matthewkmayer/calagator,cp/calagator-1,Eugator-Wranglers/calagator,nblackburn87/calagator,L2-D2/calagator,cp/calagator-1,shawnacscott/calagator,reidab/calagator,matthewkmayer/calagator,matthewkmayer/calagator,matthewkmayer/calagator,jmcduffie32/calagator,shawnacscott/calagator,iamBalaji/Calagator,jmcduffie32/calagator,eeeeeean/windchimes,alexbeeken/calagator.org,Villag/dentonator,L2-D2/calagator,dudleysr/calagator-workspace,oktober/calagator,alexbeeken/calagator.org,kerrizor/calagator,oktober/calagator,jmcduffie32/calagator