Expand Atom capabilities and Add Some Examples

Thanks for Atom!  I sought out to replace HasTraits with Atom, to remove the number of dependencies (and mental load) I need for my projects.  Plus, Atom is a lot more elegant.

I was missing the following:

```python
@observe('subatom.member')
sync_trait(self, name, object, alias = None, mutual = True, remove = False)
DelegatesTo()
```
This pull request adds support for these three things, plus some examples showing these and a few other behaviors that were not immediately obvious when I started digging in to Atom.