0.5.1 Released

# Changes
  - Fix can_bloom to compare numbers (HonzaKral)
  - Switched find_expired_indices to use datetimes and timedeltas
  - Do not try and catch unrecoverable exceptions. (HonzaKral)
  - Future proofing the use of the elasticsearch client (i.e. work with version
    1.0+ of Elasticsearch) (HonzaKral)
    Needs more testing, but should work.
  - Add tests for these scenarios (HonzaKral)