minScrollbarLength setting

I couldn't figure out the rebasing stuff so I just deleted my fork and
redid the work.  I believe I followed the contributing guidlines
correctly as well.

src/perfect-scrollbar.js

@@ -6,7 +6,8 @@
   // The default settings for the plugin
   var defaultSettings = {
     wheelSpeed: 10,
-    wheelPropagation: false
+    wheelPropagation: false,
+    minScrollbarLength: null
   };
 
   $.fn.perfectScrollbar = function (suppliedSettings, option) {
@@ -66,6 +67,13 @@
         $scrollbarY.css({right: scrollbarYRight - scrollLeft});
       };
 
+      var getSettingsAdjustedThumbSize = function (thumbSize) {
+        if (settings.minScrollbarLength) {
+          thumbSize = Math.max(thumbSize, settings.minScrollbarLength);
+        }
+        return thumbSize;
+      };
+
       var updateScrollbarCss = function () {
         $scrollbarX.css({left: scrollbarXLeft + $this.scrollLeft(), bottom: scrollbarXBottom - $this.scrollTop(), width: scrollbarXWidth});
         $scrollbarY.css({top: scrollbarYTop + $this.scrollTop(), right: scrollbarYRight - $this.scrollLeft(), height: scrollbarYHeight});
@@ -77,7 +85,7 @@
         contentWidth = $this.prop('scrollWidth');
         contentHeight = $this.prop('scrollHeight');
         if (containerWidth < contentWidth) {
-          scrollbarXWidth = parseInt(containerWidth * containerWidth / contentWidth, 10);
+          scrollbarXWidth = getSettingsAdjustedThumbSize(parseInt(containerWidth * containerWidth / contentWidth, 10));
           scrollbarXLeft = parseInt($this.scrollLeft() * containerWidth / contentWidth, 10);
         }
         else {
@@ -86,7 +94,7 @@
           $this.scrollLeft(0);
         }
         if (containerHeight < contentHeight) {
-          scrollbarYHeight = parseInt(containerHeight * containerHeight / contentHeight, 10);
+          scrollbarYHeight = getSettingsAdjustedThumbSize(parseInt(containerHeight * containerHeight / contentHeight, 10));
           scrollbarYTop = parseInt($this.scrollTop() * containerHeight / contentHeight, 10);
         }
         else {