def authenticate!
      access_token = get_access_token
    
      if @client.authorized?
        session[:access_token] = access_token.token
        session[:secret_token] = access_token.secret
        session[:user] = @client.info

        session[:user]
      else
        nil
      end
    end
def authenticate!
      access_token = get_access_token
    
      if @client.authorized?
        session[:access_token] = access_token.token
        session[:secret_token] = access_token.secret
        session[:user] = @client.info

        session[:user]
      else
        nil
      end
    end
attempts to get the access token(MUST be used after user has been redirected back from twitter)