Updated readme. Going through first chapter

ch_01/hello_world/hello_world.c

@@ -0,0 +1,14 @@
+/*
+ * Simple hello world application
+ *
+ * Author: Kun Deng
+ */
+
+#include <stdio.h>
+
+int main()
+{
+    printf("hello, world\n");
+
+    return 0;
+}