Changing examples to use makefile

- Testing a modified version of the makefile from raylib Instead of multiple project files for examples.
- Fixed readme example

Examples/models/resources/shaders/skybox.vs

@@ -0,0 +1,32 @@
+/*******************************************************************************************
+*
+*   rPBR [shader] - Background skybox vertex shader
+*
+*   Copyright (c) 2017 Victor Fisac
+*
+**********************************************************************************************/
+
+#version 330
+
+// Input vertex attributes
+in vec3 vertexPosition;
+
+// Input uniform values
+uniform mat4 projection;
+uniform mat4 view;
+
+// Output vertex attributes (to fragment shader)
+out vec3 fragPos;
+
+void main()
+{
+    // Calculate fragment position based on model transformations
+    fragPos = vertexPosition;
+
+    // Remove translation from the view matrix
+    mat4 rotView = mat4(mat3(view));
+    vec4 clipPos = projection*rotView*vec4(vertexPosition, 1.0);
+
+    // Calculate final vertex position
+    gl_Position = clipPos.xyww;
+}