Moving ESR article to intermediate level

README.md

@@ -176,6 +176,7 @@ Intermediate
 * [memcpy vs memmove][205]
 * [MPI tutorial][265]
 * [Object-Oriented Programming with ANSI C][185] (online PDF)
+* [The lost art of C structure packing][34]
 
 Advanced
 --------
@@ -186,7 +187,6 @@ Advanced
 * [Implementing smart pointers for the C programming language][240]
 * [Inline functions in C][245]
 * [Some dark corners of C][210]
-* [The lost art of C structure packing][34]
 * [What a C programmer should know about memory][271]
 * [Writing efficient C and C code optimization][33]