snappy: A+C: add Jan Mercl (Individual CLA).

R=adg, r
CC=0xjnml, golang-dev
https://codereview.appspot.com/7345047

AUTHORS

@@ -9,3 +9,4 @@
 # Please keep the list sorted.
 
 Google Inc.
+Jan Mercl <0xjnml@gmail.com>

CONTRIBUTORS

@@ -26,6 +26,7 @@
 
 # Please keep the list sorted.
 
+Jan Mercl <0xjnml@gmail.com>
 Kai Backman <kaib@golang.org>
 Marc-Antoine Ruel <maruel@chromium.org>
 Nigel Tao <nigeltao@golang.org>