fix: make reformat configurable in initialize

[AdriVanHoudt]

I didn't really see how to write a test for this but let me know if you have ideas.

Fixes https://github.com/hapijs/boom/issues/288

[devinivy]

If you'd like to pull in an old version of boom for testing purposes, you could do something like this: https://github.com/hapijs/hapi/blob/c95985e225fa09c4b640a887ccb4be46dbe265bc/package.json#L43

[kanongil]

For a test, I would probably just do something like Object.defineProperty(new Boom.Boom('oops'), 'reformat', { value: true }). It should fail on the current release, and pass with this fix.

[AdriVanHoudt]

Added the test, thanks for the nice and easy suggestion @kanongil

[devinivy]

Thanks!