fix(show): use bind hook to handle undefined values
fix(show): use bind hook to handle undefined values

Fixes aurelia/templating#100

The valueChanged hook isn't called during initial binding when themodel value is undefined because it matches the behavior property's intitial value (undefined).  Introducing the bind hook allows us to handle any initial value.

marknutter/templating-resources,cmichaelgraham/templating-resources,jdanyow/templating-resources,aurelia/templating-resources,aurelia/templating-resources,aurelia/templating-resources,hitesh97/templating-resources