Merge branch 'master' of https://github.com/ProjectMirador/mirador into 2129-reduxDebounce

__tests__/integration/mirador/companion_windows.test.js

__tests__/src/actions/canvas.test.js

__tests__/src/actions/window.test.js

__tests__/src/components/OpenSeadragonViewer.test.js

__tests__/src/lib/AnnotationResource.test.js

__tests__/src/lib/OpenSeadragonCanvasOverlay.test.js

__tests__/src/reducers/companionWindows.test.js

src/components/CompanionWindow.js

src/components/OpenSeadragonViewer.js

src/components/WindowViewer.js

src/containers/CompanionWindow.js

src/containers/OpenSeadragonViewer.js

src/lib/AnnotationResource.js

src/lib/OpenSeadragonCanvasOverlay.js

src/state/actions/canvas.js

src/state/actions/window.js

src/state/reducers/companionWindows.js