Disable Launchy using ENV variable instead of completely redefining deliver! method.

[nashby]

Since a new version of letter_opener is released and there's a change in LetterOpener::Message.rendered_messages method (now we send location using options param) letter_opener_web is broken when letter_opener_web as delivery method is used (sorry about that).

There's a bug report about it here ryanb/letter_opener#147. I think it makes sense to disable Launchy using LAUNCHY_DRY_RUN env variable (https://github.com/copiousfreetime/launchy/blob/master/lib/launchy.rb#L15) to avoid future issues with compatibilities with letter_opener gem. What do you think?

[GarrisonD]

@pseudomuto are you going to merge this PR soon?

I think plenty of developers who use latests versions of letter_opener_web and letter_opener need it.

[pseudomuto]

My apologies. I wasn't pinged here so I didn't see it. 👀

[pseudomuto]

LGTM 👍 Thanks for the fix man!