Fix to loadBranch

Hi Ludo

Thanks for the truly awesome jquery.treetable plugin!

While using it, I discovered what I think is a bug in loadBranch().  I fixed it with this small commit (at least, it's working for me now).

The problem occurs when you call loadBranch() to add subnodes to a node that has open subtrees.  Say have this tree:

    * A
    * B
       * BA
       * BB
         * BBA
         * BBB
    * C

If I call loadBranch() with node B as the first argument, to add row "D", I expect this:

    * A
    * B
       * BA
       * BB
         * BBA
         * BBB
       * D <--- new row added here
    * C

But I get this:

    * A
    * B
       * BA
       * BB
       * D   <--- new row added here
         * BBA
         * BBB
    * C


Does that make sense?

Thanks again!

Kyle (github: quile)