Add support for project deploy keys

confirm parameter (see
http://doc.gitlab.com/ee/api/users.html#user-creation). I have chosen to
not change the meaning of the method parameter because it would break
application silently. To be discussed.

The update user doesn't have a confirm parameter so remove it: it breaks
the API but it generates a compilation error so it's easily fixable

Disconnect the HTTPURLConnection after use (Fixes #59).

As the connection is not reused, we can disconnect it right away, no need
to change the GitlabAPI API.

Added various API calls:

- block/unblock user
- update project
- transfer project to a new namespace

Dependency Upgrades

* Upgraded gradle build script

* Use gradle wrapper verion 2.4
* Plugin 'maven' added to install jar to local repo
* Sources jar will also be generated

Fix crash when deleting a project

Fix name of json property

Make getMergeRequests pull all merge requests

adding user ssh key api calls and ssh key model

Fixes for issues #44 and #45

Resolved Jackson JSON Deserialization when retrieving Projects. This fixes [Issue #45](https://github.com/timols/java-gitlab-api/issues/45).

Turned off hostname verification. Fixed [Issue #44](https://github.com/timols/java-gitlab-api/issues/44).

Accept a merge request

Changed getOpenMergeRequests to only retrieve the open merge requests 

Changed getOpenMergeRequests to only retrieve the open merge requests instead of retrieving all and filtering client side. This will speedup especially old projects with lots of merge requests.

Fix LICENSE typo and updated copyright years