remove unnecessary instantiation of the helpers.Breakpoints() class
reduce the indentation
reduce the indentation
add the .after_render_all() method, improve the run_callbacs() method and update the .breackpoints propertie before call .render_all() method
add the TwitterTimeline() class and use it to insert the twitter timeline widget
remove the twitter timeline code because this is generated dynamically
add test coverage for the after_render_all() method