Updating submodule pointer to readium-shared-js for release 0.19
Updating submodule pointer to readium-shared-js for release 0.19

readium/readium-js,bibliolabs/readium-js,ravn-no/readium-js,bibliolabs/readium-js,kivuto/readium-js,kivuto/readium-js,readium/readium-js,looknear/readium-js,looknear/readium-js,ravn-no/readium-js