Use the official markdown version of the GPLv3

Change-Id: I87a0a46a976a031088c39d5ad04cb05d238f082e
diff --git a/INSTALL.md b/INSTALL.md
index a4b40e5..a527086 100644
--- a/INSTALL.md
+++ b/INSTALL.md
@@ -14,7 +14,7 @@
 
 -  ``libpcap``
 
-    Comes with the base system on OS X and macOS.
+    Comes with the base system on macOS.
 
     On Ubuntu:
 
@@ -24,8 +24,6 @@
 
 ## Build Steps
 
-Waf meta build system is used by ndn-tools.
-
 To configure, compile, and install ndn-tools, type the following commands
 in ndn-tools source directory: