Cloudant

- [NEW] Added `Cloudant.bluemix()` class method to the Cloudant client allowing service credentials
to be passed using the CloudFoundry VCAP_SERVICES environment variable.
- [FIXED] Fixed client construction in `cloudant_bluemix` context manager.
- [FIXED] Fixed validation for feed options to accept zero as a valid value.

- [FIXED] Fixed crash caused by non-UTF8 chars in design documents.
- [FIXED] Fixed `TypeError` when setting revision limits on Python>=3.6.
- [FIXED] Fixed the `exists()` double check on `client.py` and `database.py`.
- [FIXED] Fixed Cloudant exception code 409 with 412 when creating a database that already exists.
- [FIXED] Catch error if `throw_on_exists` flag is `False` for creating a document.
- [FIXED] Fixed /_all_docs call where `keys` is an empty list.
- [FIXED] Issue where docs with IDs that sorted lower than 0 were not returned when iterating
through _all_docs.

- [NEW] Added `timeout` option to the client constructor for setting a timeout on a HTTP connection
or a response.
- [NEW] Added `cloudant_bluemix` method to the Cloudant client allowing service credentials to be
passed using the CloudFoundry VCAP_SERVICES environment variable.
- [IMPROVED] Updated non-response related errors with additional status code and improved error
message for easier debugging. All non-response error are handled using either CloudantException
or CloudantArgumentError.
- [FIXED] Support `long` type argument when executing in Python 2.

- [FIXED] Resolved issue where generated UUIDs for replication documents would not be converted to
strings.
- [FIXED] Resolved issue where CouchDatabase.infinite_changes() method can cause a stack overflow.

- [FIXED] Resolved issue where the custom JSON encoder was at times not used when transforming data.
- [NEW] Added support for managing the database security document through the SecurityDocument class
and CouchDatabase convenience method `get_security_document`.
- [NEW] Added `auto_renewal` option to the client constructor to handle the automatic renewal of an
expired session cookie auth.

- [NEW] Added auto connect feature to the client constructor.
- [FIXED] Requests session is no longer valid after disconnect.