Add ability to delete an issue comment (GitLabPHP#150)

* Add ability to delete an issue comment

* Rename deleteComment to removeComment according to GitLabPHP#149

Add deploy keys related API (GitLabPHP#146)

* Add API to retrieve all deploy keys

* Add method to enable/disable a key for a project

Added test for group with vis level

Added namespace search endpoint. Fixes GitLabPHP#101

Added current_sign_in_at field to User modal

Handle dots and slashes when encoding. Fixes GitLabPHP#86 GitLabPHP#87

- Support authentication via OAuth

- Expose avatar_url in Project Model
- Refactor of project hook endpoints (breaking change)

Project sorting tests and saving group member test

Merge pull request GitLabPHP#47 from davidkuridza/bug/fix-wrong-MR-co…

…mments-endpoint

fix wrong comments endpoint for merge requests

Merge pull request GitLabPHP#45 from iamluc/master

Get file API