Upgrade sequelize and remove unique email constraints

server/migrations/20170712055148-non-unique-email.js

@@ -0,0 +1,19 @@
+module.exports = {
+  up: (queryInterface, Sequelize) => {
+    queryInterface.removeConstraint('users', 'email_unique_idx');
+    queryInterface.removeConstraint('users', 'username_unique_idx');
+  },
+
+  down: (queryInterface, Sequelize) => {
+    queryInterface.changeColumn('users', 'email', {
+      type: Sequelize.STRING,
+      unique: true,
+      allowNull: false,
+    });
+    queryInterface.changeColumn('users', 'username', {
+      type: Sequelize.STRING,
+      unique: true,
+      allowNull: false,
+    });
+  },
+};

server/migrations/20170712072234-uniq-slack-id.js

@@ -0,0 +1,13 @@
+module.exports = {
+  up: (queryInterface, Sequelize) => {
+    queryInterface.changeColumn('users', 'slackId', {
+      type: Sequelize.STRING,
+      unique: true,
+      allowNull: false,
+    });
+  },
+
+  down: (queryInterface, Sequelize) => {
+    queryInterface.removeConstraint('users', 'users_slack_id_idx');
+  },
+};