add getUser(username) and getProject(projectName) method

     // new method
     public GitlabProject getProject(String NAMESPACE_PROJECT_NAME) throws IOException {
        String tailUrl = GitlabProject.URL + "/" + NAMESPACE_PROJECT_NAME;
        return retrieve().to(tailUrl, GitlabProject.class);
      }

    // new method
    public GitlabUser getUser(String username) throws IOException {
        String tailUrl = GitlabUser.URL + "?search=" + username;
        GitlabUser[] arrays = retrieve().to(tailUrl, GitlabUser[].class);
        if (null == arrays || arrays.length == 0) return null;
        return arrays[0];
    }