Fixed Rails 4 deprecation warning re: :conditions option in has_many

DEPRECATION WARNING: The following options in your Doorkeeper::Application.has_many :authorized_tokens declaration are deprecated: :conditions. Please use a scope block instead. For example, the following:

    has_many :spam_comments, conditions: { spam: true }, class_name: 'Comment'

should be rewritten as the following:

    has_many :spam_comments, -> { where spam: true }, class_name: 'Comment'