Fix #44: Update project homepage with new build instructions

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

index.html

 
 <h3>
 <a id="manual" class="anchor" href="#manual" aria-hidden="true"><span aria-hidden="true" class="octicon octicon-link"></span></a>Manual</h3>
-
-<p><code>make &amp;&amp; make install</code></p>
+<p>We recommended downloading a versioned tarball from the relases page
+  on GitHub. Download and untar the archive:
+  </p>
+<pre>
+tar xf light-x.yy.tar.gz
+cd light-x.yy/
+./configure && make
+sudo make install
+</pre>
+<p>However, should you want to try the latest GitHub source you first
+need to clone the repository and run the autogen.sh script. This
+requires automake and autoconf to be installed on your system.</p>
+<pre>
+./autogen.sh
+./configure && make
+sudo make install
+</pre>
+<p>The configure script and Makefile.in files are not part of GIT
+because they are generated at release time with make release.</p>
 
 <p><strong>Optional:</strong> If you want to use udev rules instead of suid to manage sysfs permissions, you may skip the <code>make install</code> step and instead add something like the following to <code>/etc/udev/rules.d/90-backlight.rules</code> after copying your binaries:</p>