Allow for replacing HttpClient #VIT-2506

0.6.5-beta

* Added gzip compression for API requests.

* Raised the minimum Guzzle version to 6.2.1.
  This version addressed the HTTP_PROXY security vulnerability (CVE-2016-5385).

* Fix [contentful#9](contentful#9) Trying to retrieve fields that end with "Id" fails.

Prepare 0.6.3-beta

Prepare 0.6.2-beta

Prepare next release.

Add a link to the reference documentation