Use refute_timeout configured for all refute_ assertions (#603)
Use refute_timeout configured for all refute_ assertions (#603)

What changed?
============

All refutation test helpers in `Bamboo.Test` should be using the
`refute_timeout` configuration when testing on shared mode.

```elixir
config :bamboo, :refute_timeout, 10
```

The `refute_email_delivered_with/1` macro was not using the
configuration, but instead it had a hardcoded 100ms. We update it to use
the `refute_timeout`, since not using it was a bug.

Finally, the `refute_timeout/0` function currently returns 0ms when
Bamboo isn't on shared mode. We change that to be 100ms to match the
previously hardcoded value in `refute_email_delivered_with/1` and to
match the [default `refute_receive_timeout` from
ExUnit](https://hexdocs.pm/ex_unit/ExUnit.html#configure/1-options).
thoughtbot/bamboo