Remove dependency on Guzzle HTTP client

* src/HAB/Pica/Auth/LOAN3WebAuthentication.php (getClient): Removed.
  (authenticate): Use sendRequest() to send http request.
  ($client): Removed.
* src/HAB/Pica/Auth/LBSAuthentication.php (getClient): Removed.
  (authenticate): Use sendRequest() to send http request.
  ($client): Removed.
* src/HAB/Pica/Auth/AbstractHttpAuthentication.php: New
  class. Abstract base class of http based authentication modules,
  implements sendRequest().