Add comment and desired structure to colors patch

Per request from dnschnur (flot/flot#1034 (comment)), I have: 
- Added a comment explaining the purpose of the new check/override
- Changed the structure to match preferred standard structure

jquery.flot.js

@@ -642,7 +642,11 @@ Licensed under the MIT license.
 
             $.extend(true, options, opts);
 
-            if (opts.colors) options.colors = opts.colors;
+            //Override options.colors after $.extend if user has set colors, because extend does not clear out excess
+            //default colors if user defines color palette smaller than default palette size (currently 5).
+            if (opts.colors) {
+            	options.colors = opts.colors;
+            }
 
             if (options.xaxis.color == null)
                 options.xaxis.color = $.color.parse(options.grid.color).scale('a', 0.22).toString();