Adding Yosemite platform

Author: barancev

java/client/src/org/openqa/selenium/Platform.java

@@ -107,6 +107,17 @@ public String toString() {
     }
   },
 
+  YOSEMITE("yosemite", "os x 10.10") {
+    @Override
+    public Platform family() {
+      return MAC;
+    }
+    @Override
+    public String toString() {
+      return "OS X 10.10";
+    }
+  },
+
   /**
    * Many platforms have UNIX traits, amongst them LINUX, Solaris and BSD.
    */