start on a  class to handle the hash file
add a function to add the file hashes.
hook up option to compute file hashes.
Bundle Hashing Integration Tests

Adds tests verifying that the bundle hash file is generated correctly
when the option to compute hashes is specified.
Ensure output directory

Double check in the integration test that nothing gets put in the main
directory.
Merge pull request #2 from Andrew-Hagedorn-ZocDoc/BundleHashing

Bundle hashing