Add example for scaled buffers

examples/scaled_buffer.rs

@@ -0,0 +1,19 @@
+extern crate mini_gl_fb;
+
+use mini_gl_fb::Config;
+
+fn main() {
+    let mut fb = mini_gl_fb::get_fancy(Config {
+        window_title: "Hello world!",
+        window_size: (800.0, 600.0),
+        buffer_size: (2, 2),
+        .. Default::default()
+    });
+
+    let mut buffer = vec![[128u8, 0, 0, 255]; 4];
+    buffer[3] = [255, 255, 255, 255];
+
+    fb.update_buffer(&buffer);
+
+    fb.persist();
+}