Added folder structure for data

Nothing in the data folders should be commited to the repository. The
folders are only given so that we can all write scripts that clean data
with consistent conventions.

Data should be placed in the raw folder in its original form. Data that
has already been processed should be put in the processed folder. The
script that did the processing should be put in the scripts folder.

The scripts should be committed to the repository. In each scripts,
there should be information (in the form of comments) which tells where
to find the data. That way others can download the same raw data to
their raw folder and run the script to get the same processed data.