Implement the sidebar.
Delegate events each render.
Add dot for unsaved changes.
Styling notebook sidebar.
Add a class for the active persistence item in the sidebar.
Merge branch 'notebook-sidebar' of github.com:mulesoft/api-notebook into notebook-sidebar

* 'notebook-sidebar' of github.com:mulesoft/api-notebook:
  Styling notebook sidebar.
Merge pull request #145 from mulesoft/notebook-sidebar

Notebook sidebar