docs: Updating the list of ndn-cxx contributors

Change-Id: Ia2ac7efbcb7584805b4763e75129a7fb7f8d2064
diff --git a/AUTHORS.md b/AUTHORS.md
index 1238782..3760340 100644
--- a/AUTHORS.md
+++ b/AUTHORS.md
@@ -27,3 +27,6 @@
 * Jeff Burke            <http://remap.ucla.edu/jburke/>
 * Xiaoke Jiang          <http://netarchlab.tsinghua.edu.cn/~shock/>
 * Jiewen Tan            <alanwake@ucla.edu>
+* Vince Lehman          <http://vslehman.com>
+* Mathias Gibbens       <gibmat@cs.arizona.edu>
+* Chengyu Fan           <chengyu@cs.colostate.edu>