ENH: Download binary data inputs with REST.

Download the binary data inputs from the Midas server and cache
locally.  A manifest of filename, md5sum is stored in a json file.
They are downloaded into the "Data" directory, and their hash checked
which the downloaddata.py script is executed or imported as a module.

The foldermd5sums.py script can be used to conveniently regenerate the
manifest.

'import downloaddata' script is added to the notebooks that need data.
ENH: Ignore vim .swp files.
ENH: Allow directory of files to be indexed

In the Data directory, there may be sub-directories of files that need to
be kept separate, but all of them need to be indexed.
ENH: Added more files to hash.
ENH: Improved flexibility of the data download

Multiple midas servers can be searched for the files.
A progress bar was added for downloading the data.
ENH: Updated data download mechanism to be dynamic

Download data automatically as needed in notebooks,
by retrieving and caching the data in a local repository.
ENH: Ignore temp files written to this data directory.