Merge pull request #844 from metabase/history-books

resources/migrations/010_add_revision_table.yaml

resources/migrations/liquibase.json

src/metabase/api/card.clj

src/metabase/api/dash.clj

src/metabase/api/revision.clj

src/metabase/api/routes.clj

src/metabase/api/user.clj

src/metabase/db/internal.clj

src/metabase/models/dashboard.clj

src/metabase/models/revision.clj

src/metabase/models/revision/diff.clj

src/metabase/models/user.clj

test/metabase/api/revision_test.clj

test/metabase/models/revision/diff_test.clj

test/metabase/models/revision_test.clj