first pass at adding Crosswalk support
first pass at adding Crosswalk support

tony--/cordova-screenshot,ismaeldcom/cordova-screenshot,agrande/cordova-screenshot,tony--/cordova-screenshot,agrande/cordova-screenshot,zhuyongyong/cordova-screenshot,ismaeldcom/cordova-screenshot,zhuyongyong/cordova-screenshot,firsara/cordova-screenshot,firsara/cordova-screenshot