Updated colorpicker.js

Added support of specifying trigger control to pop up colour picker at right position.
Depends on new dummy css classes: 
color-picker: Specifying the container.
color-picker-trigger: Specifying the control which pop up colour picker.
Usage:
<div class="input-group color-picker"> <!-- the container -->
  <span class="input-group-addon">Front Color</span> <!-- preceding label -->
  <input type="text" class="form-control"> <!-- show colour value -->
  <span class="input-group-addon color-picker-trigger"><!-- the trigger control -->
    <i></i><!-- show colour block -->
  </span>
</div>