Improve the README

[starkos]

A few changes I'd like to make to the README next time I'm in there:

• Link to usage examples in Industrious.ToDo; see Industrious.Mvvm for an example
• Fix layout and highlighting of second AutoFocusBehavior code sample
• Change "for those times you'd like to bind an object's visibility to the existence of an object" to "for those times you'd like to bind the visibility of a view to the existence of an object"