Compatibility with the latest changes in commanded

[ImmaculatePine]

I tried to use some new features of commanded with extreme adapter and found out that they are incompatible.

So, there is what I did in this PR:

• Added child_spec/0 and subscribe_to/4 functions required by the new behaviour
• Added support for transient subscriptions to all streams
• Copied adapter tests from commanded/test/support and tweaked them
• Made sure that tests can start/stop Docker container with Event Store
• Updated dependencies (including commanded itself, which will change after its release)

What I'd like to do in the next PRs:

• add support for missing parts from the newest features (look for @tag skip: ... and @todo comments)
  • :no_stream and :stream_exists parameters for append_to_stream
  • find a better way of handling event_number (does global event number make any sense in Event Store?)
  • allow persistent subscriptions to the streams that are not projections
  • unsubscribe by PID instead of subscription name like it is documented in commanded
• get rid of copy-pasted tests and use the original test cases as I did it in snapshot_test.exs
• try to make restarts between tests faster (stop/start container instead of kill -> delete -> create?)
• start using formatter in this repo

Let me know if you're interested in further development of this library and the above steps sound like a plan. :)

[slashdotdash]

@ImmaculatePine Really sorry to have wasted your time, but I've already done the work to upgrade this adapter to support Commanded's next release in the feature/commanded-vnext branch. I thought I had already merged the changes into master, but hadn't.

[ImmaculatePine]

@slashdotdash Haha, I was pretty sure that this library was abandoned. :D Good to know that I was wrong. At least I had a chance to learn how it works from inside.