0.14.0

• Fixes bug where primary key specified by user was not being checked in some
  POST requests and some search queries.
• #223: documents CORS example.
• #280: don't expose raw SQL in responses on database errors.
• #299: show error message if search query tests for NULL using comparison
  operators.
• #315: check for query object being None.
• #324: DELETE should only return 204 if
  something is actually deleted.
• #325: support null inside has search operators.
• #328: enable automatic testing for Python 3.4.
• #333: enforce limit in helpers.count.
• #338: catch validation exceptions when attempting to update relations.
• #339: use user-specified primary key on PATCH requests.
• #344: correctly encodes Unicode fields in responses.