Note 1.8 as the oldest supported version

Doc/Manual/Ruby.html

@@ -147,7 +147,7 @@
 <H2><a name="Ruby_nn2"></a>38.1 Preliminaries</H2>
 
 
-<p> SWIG 1.3 is known to work with Ruby versions 1.6 and later.
+<p> SWIG 3.0 is known to work with Ruby versions 1.8 and later.
 Given the choice, you should use the latest stable version of Ruby. You
 should also determine if your system supports shared libraries and
 dynamic loading. SWIG will work with or without dynamic loading, but
@@ -191,7 +191,7 @@ header file. This file is usually contained in a directory such as </p>
 
 <div class="code shell diagram">
 <pre>/usr/lib/ruby/1.8/x86_64-linux-gnu/ruby.h
-/usr/local/lib/ruby/1.6/i686-linux/ruby.h
+/usr/include/ruby-2.1.0/ruby.h
 </pre>
 </div>
 
@@ -201,8 +201,14 @@ installed, you can run Ruby to find out. For example: </p>
 
 <div class="code shell">
 <pre>$ ruby -e 'puts $:.join("\n")'
-/usr/local/lib/ruby/site_ruby/1.6 /usr/local/lib/ruby/site_ruby/1.6/i686-linux
-/usr/local/lib/ruby/site_ruby /usr/local/lib/ruby/1.6 /usr/local/lib/ruby/1.6/i686-linux .
+/usr/local/lib/site_ruby/2.1.0
+/usr/local/lib/x86_64-linux-gnu/site_ruby
+/usr/local/lib/site_ruby
+/usr/lib/ruby/vendor_ruby/2.1.0
+/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.1.0
+/usr/lib/ruby/vendor_ruby
+/usr/lib/ruby/2.1.0
+/usr/lib/x86_64-linux-gnu/ruby/2.1.0
 </pre>
 </div>
 
@@ -260,7 +266,7 @@ operating system would look something like this: </p>
 <div class="code shell">
 <pre>$ swig -ruby example.i
 $ gcc -O2 -fPIC -c example.c
-$ gcc -O2 -fPIC -c example_wrap.c -I/usr/local/lib/ruby/1.6/i686-linux
+$ gcc -O2 -fPIC -c example_wrap.c -I/usr/include/ruby-2.1.0
 $ gcc -shared example.o example_wrap.o -o example.so
 </pre>
 </div>
@@ -334,7 +340,7 @@ using the C++ compiler. For example: </p>
 <pre>
 $ swig -c++ -ruby example.i
 $ g++ -fPIC -c example.cxx
-$ g++ -fPIC -c example_wrap.cxx -I/usr/local/lib/ruby/1.6/i686-linux
+$ g++ -fPIC -c example_wrap.cxx -I/usr/include/ruby-2.1.0
 $ g++ -shared example.o example_wrap.o -o example.so
 </pre>
 </div>
@@ -4466,7 +4472,7 @@ and then type <tt>make</tt> to build the shared library: </p>
 <pre>$ <b>ruby extconf.rb</b>
 creating Makefile
 $ <b>make</b>
-g++ -fPIC -g -O2 -I. -I/usr/local/lib/ruby/1.7/i686-linux \
+g++ -fPIC -g -O2 -I. -I/usr/include/ruby-2.1.0 \
 -I. -c shape_wrap.cxx
 gcc -shared -L/usr/local/lib -o shape.so shape_wrap.o -L. \
 -lruby -lruby -lc</pre>