Changeset 6683 for trunk/examples/zoo/loader2

adding an example of using a loader to allow users to chose an example excel spreadsheet or upload their own. the uploaded file data is stored in the driver.xml. the simulation checks whether the user chose an example excel spreadsheet or uploaded thier own. if the user uploaded their own file, we write it to disk, then parse it using a pandas dataframe and finally load it into a Rappture Curve.