correct stroke width type"

src/components/stroke-width-indicator.jsx

@@ -23,7 +23,7 @@ const StrokeWidthIndicatorComponent = props => (
 
 StrokeWidthIndicatorComponent.propTypes = {
     onChangeStrokeWidth: PropTypes.func.isRequired,
-    strokeWidth: PropTypes.string.isRequired
+    strokeWidth: PropTypes.number.isRequired
 };
 
 export default StrokeWidthIndicatorComponent;

src/containers/brush-mode.jsx

@@ -80,7 +80,7 @@ BrushMode.propTypes = {
     colorState: PropTypes.shape({
         fillColor: PropTypes.string.isRequired,
         strokeColor: PropTypes.string.isRequired,
-        strokeWidth: PropTypes.string.isRequired
+        strokeWidth: PropTypes.number.isRequired
     }).isRequired,
     handleMouseDown: PropTypes.func.isRequired,
     isBrushModeActive: PropTypes.bool.isRequired,

src/containers/line-mode.jsx

@@ -272,7 +272,7 @@ LineMode.propTypes = {
     colorState: PropTypes.shape({
         fillColor: PropTypes.string.isRequired,
         strokeColor: PropTypes.string.isRequired,
-        strokeWidth: PropTypes.string.isRequired
+        strokeWidth: PropTypes.number.isRequired
     }).isRequired,
     handleMouseDown: PropTypes.func.isRequired,
     isLineModeActive: PropTypes.bool.isRequired,