change circle radius percentage calculation

Change circle radius  percentage calculation.
Add example for percentage props for shape.
Remove unused document ref

Example/examples/Circle.js

@@ -11,12 +11,12 @@ class CircleExample extends Component{
     render() {
         return <Svg
             height="100"
-            width="100"
+            width="140"
         >
             <Circle
-                cx="50"
-                cy="50"
-                r="50"
+                cx="50%"
+                cy="50%"
+                r="40%"
                 fill="pink"
             />
         </Svg>;

Example/examples/Ellipse.js

@@ -14,10 +14,10 @@ class EllipseExample extends Component{
             width="110"
         >
             <Ellipse
-                cx="55"
-                cy="55"
-                rx="50"
-                ry="30"
+                cx="50%"
+                cy="50%"
+                rx="45%"
+                ry="30%"
                 stroke="purple"
                 strokeWidth="2"
                 fill="yellow"

Example/examples/Line.js

@@ -15,10 +15,10 @@ class LineExample extends Component{
             width="100"
         >
             <Line
-                x1="0"
-                y1="0"
-                x2="100"
-                y2="100"
+                x1="10%"
+                y1="10%"
+                x2="90%"
+                y2="90%"
                 stroke="red"
                 strokeWidth="2"
             />

Example/examples/Rect.js

@@ -14,10 +14,10 @@ class RectExample extends Component{
             height="60"
         >
             <Rect
-                x="25"
-                y="5"
-                width="150"
-                height="50"
+                x="5%"
+                y="5%"
+                width="90%"
+                height="90%"
                 fill="rgb(0,0,255)"
                 strokeWidth="3"
                 stroke="rgb(0,0,0)"