added Demo.concave, added Bodies.fromVertices, added Vertices.isConvex, fixed compound properties

Author: liabru

demo/dev.html

@@ -6,6 +6,9 @@
         <meta name="viewport" content="width=device-width,minimal-ui">
         <meta name="robots" content="noindex">
 
+        <!-- only required if using Bodies.fromVertices with concave vertices -->
+        <script type="text/javascript" src="./js/lib/decomp.js"></script>
+
         <!-- only required if using Matter.RenderPixi -->
         <script type="text/javascript" src="./js/lib/pixi.dev.js"></script>
 
@@ -32,6 +35,7 @@ <h1>Matter.js Demo (Dev. Build)</h1>
                     <option value="mixed">Mixed Shapes</option>
                     <option value="mixedSolid">Solid Rendering</option>
                     <option value="compound">Compound Bodies</option>
+                    <option value="concave">Concave Bodies</option>
                     <option value="newtonsCradle">Newton's Cradle</option>
                     <option value="wreckingBall">Wrecking Ball</option>
                     <option value="slingshot">Slingshot Game</option>

demo/js/Demo.js

@@ -130,8 +130,6 @@
         });
 
         World.add(_world, compound);
-
-        _world.gravity.y = 1;
 
         var renderOptions = _engine.render.options;
         renderOptions.showCollisions = true;
@@ -141,6 +139,26 @@
         renderOptions.showConvexHulls = true;
     };
 
+    Demo.concave = function() {
+        var _world = _engine.world;
+
+        Demo.reset();
+
+        var vertices = Matter.Vertices.fromPath('354 89,336 118,310 145,302 227,322 271,375 292,490 289,539 271,540 233,549 133,526 100,552 36,601 63,633 122,628 227,594 304,505 340,426 340,327 330,265 294,246 242,246 181,256 133,283 81,346 44');
+        //var vertices = Matter.Vertices.fromPath('164 171,232 233,213 302,273 241,342 305,316 231,364 170,309 188,281 117,240 182');
+
+        var concave = Bodies.fromVertices(200, 200, vertices);
+        World.add(_world, concave);
+
+        var renderOptions = _engine.render.options;
+        renderOptions.showCollisions = true;
+        renderOptions.showBounds = true;
+        renderOptions.showAxes = true;
+        renderOptions.showPositions = true;
+        renderOptions.showConvexHulls = true;
+        //renderOptions.showVertexNumbers = true;
+    };
+
     Demo.slingshot = function() {
         var _world = _engine.world;