Merge branch 'master' into iframecomm

__tests__/src/actions/canvas.test.js

__tests__/src/components/ThumbnailNavigation.test.js

__tests__/src/components/ViewerNavigation.test.js

__tests__/src/selectors/canvases.test.js

package.json

src/components/ThumbnailNavigation.js

src/components/ViewerNavigation.js

src/containers/ThumbnailNavigation.js

src/containers/ViewerNavigation.js

src/lib/CanvasGroupings.js

src/state/actions/canvas.js

src/state/selectors/canvases.js