docs: update supported platforms for Ubuntu 17.10 and macOS 10.13

Change-Id: Ie073ba5b6f56510a9fac355d77a34c0fb44bcac1
diff --git a/docs/INSTALL.rst b/docs/INSTALL.rst
index fcf1865..f9041e0 100644
--- a/docs/INSTALL.rst
+++ b/docs/INSTALL.rst
@@ -9,12 +9,12 @@
 ndn-cxx uses continuous integration and has been tested on the following
 platforms:
 
--  Ubuntu 14.04 (64-bit and 32-bit)
+-  Ubuntu 14.04 (64-bit)
 -  Ubuntu 16.04 (64-bit and 32-bit)
--  Ubuntu 17.04 (64-bit and 32-bit)
--  OS X 10.10
+-  Ubuntu 17.10 (64-bit)
 -  OS X 10.11
 -  macOS 10.12
+-  macOS 10.13
 
 ndn-cxx is known to work on the following platforms, although they are not officially
 supported: