A+C: add Sam Zaydel

For gonum/plot#370.
diff --git a/AUTHORS b/AUTHORS
index afb6d90..efe6d63 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -38,6 +38,7 @@
 Renée French
 Robin Eklind <r.eklind.87@gmail.com>
 Samuel Kelemen <Samuel@Kelemen.us>
+Sam Zaydel <szaydel@gmail.com>
 Scott Holden <scott@sshconnection.com>
 Sebastien Binet <seb.binet@gmail.com>
 Shawn Smith <shawnpsmith@gmail.com>
diff --git a/CONTRIBUTORS b/CONTRIBUTORS
index d722c40..e792fcd 100644
--- a/CONTRIBUTORS
+++ b/CONTRIBUTORS
@@ -45,6 +45,7 @@
 Renée French
 Robin Eklind <r.eklind.87@gmail.com>
 Samuel Kelemen <Samuel@Kelemen.us>
+Sam Zaydel <szaydel@gmail.com>
 Scott Holden <scott@sshconnection.com>
 Sebastien Binet <seb.binet@gmail.com>
 Shawn Smith <shawnpsmith@gmail.com>