Add crypto to extra_application

[nallwhy]

Thie PR removes compile warning below

==> elixir_uuid
Compiling 1 file (.ex)
warning: :crypto.hash/2 defined in application :crypto is used by the current application but the current application does not depend on :crypto. To fix this, you must do one of:

  1. If :crypto is part of Erlang/Elixir, you must include it under :extra_applications inside "def application" in your mix.exs

  2. If :crypto is a dependency, make sure it is listed under "def deps" in your mix.exs

  3. In case you don't want to add a requirement to :crypto, you may optionally skip this warning by adding [xref: [exclude: [:crypto]]] to your "def project" in mix.exs

Found at 2 locations:
  lib/uuid.ex:589: UUID.namebased_uuid/2
  lib/uuid.ex:593: UUID.namebased_uuid/2

warning: :crypto.strong_rand_bytes/1 defined in application :crypto is used by the current application but the current application does not depend on :crypto. To fix this, you must do one of:

  1. If :crypto is part of Erlang/Elixir, you must include it under :extra_applications inside "def application" in your mix.exs

  2. If :crypto is a dependency, make sure it is listed under "def deps" in your mix.exs

  3. In case you don't want to add a requirement to :crypto, you may optionally skip this warning by adding [xref: [exclude: [:crypto]]] to your "def project" in mix.exs

Found at 3 locations:
  lib/uuid.ex:383: UUID.uuid4/1
  lib/uuid.ex:560: UUID.uuid1_clockseq/0
  lib/uuid.ex:583: UUID.uuid1_node/1

[ftes]

Why was this not merged?

I have the same warning.

[ftes]

See #56 I guess.