Update copyright years

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

index.html

         <h1>
 <a id="light" class="anchor" href="#light" aria-hidden="true"><span aria-hidden="true" class="octicon octicon-link"></span></a>Light</h1>
 
-<p>Copyright (C) 2012 - 2014, Fredrik Haikarainen
+<p>Copyright (C) 2012 - 2018, Fredrik Haikarainen
 This is free software, see the source for copying conditions.  There is NO
 warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE</p>