added blurb about reading stuff

INSTALL

@@ -6,6 +6,10 @@ would type "make sunos" to build sudo for SunOS 4.x.  If your OS is not
 in the list try the generic entry.  You may have to add your own OS entry
 in the Makefile, it's not hard to do.
 
+    You should read the Makefile and sudo.h carefully and determine which
+options are applicable to your site and your needs.  (Although USE_INSULTS
+is not defined by default it is highly recommended :-)
+
     To install sudo on your system type "make install" -- this will install
 sudo and visudo binaries, the sudo man page, and a sample sudoers file
 (if one does not already exist).  You can also install various pieces of