Documentation Update

- Cygwin doesn't support all color combinations, which include bold,
  underline and bright background colors.  Added a troubleshooting
  item that describes this problem, and suggests running "task colors"
  to determine just which colors are supported.

html/troubleshooting.html

@@ -83,6 +83,24 @@
                 </p>
               </div>
 
+              <br />
+              <h2 class="title">Do colors work under Cygwin?</h2>
+              <div class="content">
+                <p>
+                  They do, but only in a limited way.  You can use regular
+                  foreground colors (black, red, green ...) and you can
+                  regular background colors (on_black, on_red, on_green ...),
+                  but underline and bold are not supported.
+                </p>
+
+                <p>
+                  If you run the command:
+                  <code><pre>% task colors</pre></code>
+                  Task will display all the colors it can use, and you will
+                  see which ones you can use.
+                </p>
+              </div>
+
               <br />
               <br />
               <div class="content">