[WIP] Add ExampleTests

#11: Adding tests for the core Example class.

(Not ready to merge yet.)

When testing the behaviour of `Example.name` I found that it only included the immediate parent group's name, rather than all nested parents like I expected. I've made the change, but if it turns out that was the expected behaviour I'm happy to revert it.
`group.name` walks up the example group stack to determine its name, so this should work.

> When testing the behaviour of `Example.name` I found that it only included the immediate parent group's name

Really? Looking at the test output this doesn't seem to be the case. Do you mean that `"root example group"` isn't included? That's by design.