Add fixity for (<#) (#>) combinators

[dmjio]

• Refactor examples to take advantage of fixity changes
• Use defaultApp smart constructor with examples

-- dmj: bind tightest to the `model` portion
infixl 0 <#
infixr 0 #>

This allows convenient syntax like

m { uri = newUri } <# NoOp <$ pushURI u

and

m - 1 <# consoleLog "substracting" >> pure NoOp

with requiring parens