split transport_opts into tcp_opts and tls_opts for gun2

[phunehehe]

This makes shotgun compatible with gun v2 (and incompatible with gun v1)
gun v2 has been in RC for a while now
#193

[elbrujohalcon]

Hi @phunehehe … I'm merging this one now and I invited you to be a maintainer of this repository so you can push changes to it, publish it on hex.pm and do whatever else you need with it :)

[phunehehe]

Thanks!
I have accepted the invite. I don't have any plan for the near future but let's see :)

[beligante]

Good Morning shotgun team!

Are you guys open to drafting a release for this update? I'm pointing to the latest master ref, but my project requires official releases - for regulatory purposes. Thanks In advance

[phunehehe]

@beligante I took the liberty to make a 1.0.0 release. Not sure if anything else is needed, I'm not familiar with the release process. I'm using it in production, but I'm marking it pre-release anyway as a precaution.

[elbrujohalcon]

Release away, @phunehehe !! Go for it!
You folks are the most prominent (and quite possibly the only) real users of this library.
Do whatever you see fit with it.

[phunehehe]

@elbrujohalcon This library is used by launchdarkly/erlang-server-sdk which is somewhat popular and active. It's the only thing that requires Gun 1 in my system and that was why I ended up here
I bet there are other silent users as well :)