add No Silver Bullet to readme

I'm not sure about the licensing, so I'm adding it to the readme.

Author: samlecuyer

design/README.md

@@ -1,6 +1,6 @@
 # Design
-
+* [No Silver Bullet — Essence and Accidents of Software Engineering](http://faculty.salisbury.edu/~xswang/Research/Papers/SERelated/no-silver-bullet.pdf)
 * [Traits: A Mechanism for Fine-Grained Reuse](http://scg.unibe.ch/archive/papers/Duca06bTOPLASTraits.pdf)
 
 * :scroll: [Out of the Tar Pit](out-of-the-tar-pit.pdf)
-    > We identify common causes of complexity and discuss general approaches which can be taken to eliminate them where they are accidental in nature.
+    > We identify common causes of complexity and discuss general approaches which can be taken to eliminate them where they are accidental in nature.