Change models, new migrations, fix front and make tests work

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

priv/repo/migrations/20180109170315_create_users.exs

@@ -0,0 +1,16 @@
+defmodule Eventos.Repo.Migrations.CreateUsers do
+  use Ecto.Migration
+
+  def change do
+    create table(:users) do
+      add :email, :string, null: false
+      add :role, :integer, default: 0, null: false
+      add :password_hash, :string, null: false
+      add :account_id, references(:accounts, on_delete: :delete_all), null: false
+
+      timestamps()
+    end
+
+    create unique_index(:users, [:email])
+  end
+end