update build instructions

README.md

@@ -5,29 +5,12 @@
 ## Mac OS X
 
 ```
-make
+mkdir xcode
+cd xcode
+cmake .. -G Xcode
 ```
 
-
-## Emscripten
-
-```
-emmake make emscripten
-```
-
-Note that mousewheel support requires a hacked emscripten:
-
-In `src/library_glfw.js`, replace the first part of the mousewheel function with
-
-```js
-      GLFW.wheelPos = (event.detail || -event.deltaY);
-```
-
-In `system/include/GL/glfw.h`, replace the wheel callback typedef with
-
-```c
-typedef void (GLFWCALL * GLFWmousewheelfun)(float);
-```
+Then open the xcode project and build.