third: Add option for which container to append the color picker to.

This allows you to select the container that the color picker should
append to and therefore be absolutely positioned in accordance with.

This still defaults to document body, which was the previously default
container to append the color picker to.

static/third/spectrum/spectrum.js

@@ -32,7 +32,10 @@
         showAlpha: false,
         theme: "sp-light",
         palette: ['fff', '000'],
-        selectionPalette: []
+        selectionPalette: [],
+
+        // user-specified container
+        container: null
     },
     spectrums = [],
     IE = !!/msie/i.exec( window.navigator.userAgent ),
@@ -165,7 +168,7 @@
             draggingClass = "sp-dragging";
 
         var doc = element.ownerDocument,
-            body = doc.body,
+            body = opts.container || doc.body,
             boundElement = $(element),
             container = $(markup, doc).addClass(theme),
             dragger = container.find(".sp-color"),