feat(jqmFlip): Add handling of boolean and default values

The on and off values `true` and `false` are parsed and bound as boolean
values. Furthermore if no on and off values are set on will be bound to
`true` and off to `false`.
Default values are requested in #71 with general reference to the docs. 
I couldn't find a section talking about default values nevertheless I think 
this is a useful extension.

This should resolve #71