Bind a local variable correctly.

* twittering-mode.el: Bind a local variable correctly.
(twittering-call-api-with-account-in-api1.1): correctly bind the
variable `spec-string' used.
Fix the function parsing timelines related to direct messages.

* twittering-mode.el: Fix the function parsing timelines related
to direct messages with the Twitter REST API v1.1.
(twittering-http-get-default-sentinel): call the function
`twittering-json-object-to-a-status-on-direct-messages' correctly
when using the Twitter REST API v1.1.
Invoke an API with an authentication header correctly.

* twittering-mode.el: Correctly add an authentication header for
the command `get-service-configuration' with the Twitter REST API
v1.1.
(twittering-call-api-with-account-in-api1.1): fix a path for the
command `get-service-configuration' and add an authentication
header correctly.
Confirm that `json.el' and SSL are available for the new API.

* twittering-mode.el: Confirm that `json.el' and SSL are available
before calling the Twitter REST API v1.1.
(twittering-call-api-with-account): confirm that `json.el' and SSL
are available for the Twitter REST API v1.1.