Nested 'temp' creating some unexpected behavior

In our tests, we make use of rspec's before/after/around lifecycle hooks to set the state of the test, including configatron settings with `configatron.temp`. Unfortunately when you have multiple `configatron.temp` competing with each other (one wrapping the other basically), it produces some results that we didn't expect:

```
[3] pry(main)> configatron.foo = 1
1
[4] pry(main)> configatron.temp do
[4] pry(main)* configatron.foo = 2
[4] pry(main)* configatron.temp do
[4] pry(main)* configatron.foo = 3
[4] pry(main)* end
[4] pry(main)* end
3
[5] pry(main)>
[6] pry(main)> configatron.foo
2
```

In this example, our our tests assumed that the settings would be returned to their original state, which in this example would be `configatron.foo = 1`

Is there a more elegant way to achieve what we want here with `temp`? In the short term, we've restored to manually holding the state of the variable we are setting and then resetting it at the end of the `before`/`around` block

Start by reproducing the nested configatron.temp example and then trace the temp implementation and its existing tests. Check how nested RSpec before/after/around usage restores state; done means an inner temp scope does not overwrite the outer scope's eventual restoration, returning configatron.foo to its original value.

Written by the indexing model from the issue text.