feat(accordion): Transition and attribute improvements

Add support for open and close CSS transitions.
Add support for optional is-open attribute on <accordion-group> directive
Remove isolate scope from <accordion> directive
feat(collapse): Add basic collapse directive
refact(accordion): Use collapse directive to simplify accordion directive
doc(accordion): Update readme and demo
chore(accordion) : Remove test dump from accordion
fix(accordion): Use template for accordion directive
fix(accordion): Complete change to heading from title