Support Ecto 3.2.0

[jayjun]

Ecto 3.2.0 requires two new Ecto.Type callbacks, embed_as/1 and equal?/2.

warning: function embed_as/1 required by behaviour Ecto.Type is not implemented (in module Ecto.ULID)
  lib/ecto/ulid.ex:1: Ecto.ULID (module)

warning: function equal?/2 required by behaviour Ecto.Type is not implemented (in module Ecto.ULID)
  lib/ecto/ulid.ex:1: Ecto.ULID (module)

use Ecto.Type was also added to provide default implementations of those callbacks.

This pull request adds those implementations to Ecto.ULID until Ecto 3.2.0 is required.

[markusfeyh]

@jayjun could you update the tests so CI passes?

[jayjun]

@markusfeyh Hi there, appreciate you looking into this.

CI was failing because Travis couldn’t fetch certain Erlang versions. Fixed and expanded coverage up to Elixir 1.11. For your convenience, #7, #8 and half of #10 are duplicates.

[yasmin-ravenwolfe]

@TheRealReal @markusfeyh What's the status on this being merged? Another library I'm using is requiring Ecto 3.4, so I also needed to fork @jayjun's branchh to keep using ecto-ulid. I'm available to help get this into master, so let me know what I can do, thanks!

[ykurtbas]

could we please get an official version that supports Ecto 3.X branch? I am depending on people's forks.

[markusfeyh]

@ykurtbas merged and created a tag to reference:
https://github.com/TheRealReal/ecto-ulid/releases/tag/v0.3.0

[jayjun]

@markusfeyh Thanks for merging. Can you publish 0.3.0 to Hex now? See https://hex.pm/packages/ecto_ulid.