Compress puppet tarball more

- Use xz on Linux, bzip2 elsewhere (bzip2 is a bit better than gzip, and xz
is more than twice as good as bzip2).  tar can figure out what compression
has been used automatically
Merge branch 'master' into compress-puppet-more
Merge pull request #64 from InsolvencyService/compress-puppet-more

Compress puppet tarball more
Merge pull request #66 from InsolvencyService/ip-dashboard

Add employer_id column to Claim model and other refactorings
Add and configure logging

- To log from within the app, use something like:
  `app.logger.warning("Something bad happened")`

- Anything at INFO or higher will be logged
  - So DEBUG will be silently ignored
Merge pull request #68 from InsolvencyService/logging

Add and configure logging
Refactor imports in claim service