Make `project_id` and `environment_id` nullable

This is done to make belongs_to with required to properly validate association.
Otherwise `ActiveRecord::StatementInvalid` is raised.

db/migrate/20160610204157_add_deployments.rb

@@ -7,8 +7,8 @@ class AddDeployments < ActiveRecord::Migration
   def change
     create_table :deployments, force: true do |t|
       t.integer  :iid,            null: false
-      t.integer  :project_id,     null: false
-      t.integer  :environment_id, null: false
+      t.integer  :project_id
+      t.integer  :environment_id
       t.string   :ref,            null: false
       t.boolean  :tag,            null: false
       t.string   :sha,            null: false

db/schema.rb

@@ -385,8 +385,8 @@ ActiveRecord::Schema.define(version: 20160610301627) do
 
   create_table "deployments", force: :cascade do |t|
     t.integer  "iid",             null: false
-    t.integer  "project_id",      null: false
-    t.integer  "environment_id",  null: false
+    t.integer  "project_id"
+    t.integer  "environment_id"
     t.string   "ref",             null: false
     t.boolean  "tag",             null: false
     t.string   "sha",             null: false
@@ -413,7 +413,7 @@ ActiveRecord::Schema.define(version: 20160610301627) do
   add_index "emails", ["user_id"], name: "index_emails_on_user_id", using: :btree
 
   create_table "environments", force: :cascade do |t|
-    t.integer  "project_id", null: false
+    t.integer  "project_id"
     t.string   "name",       null: false
     t.datetime "created_at"
     t.datetime "updated_at"

spec/services/create_deployment_service_spec.rb

@@ -10,6 +10,7 @@ describe CreateDeploymentService, services: true do
     let(:params) do
       { environment: 'production',
         ref: 'master',
+        tag: false,
         sha: '97de212e80737a608d939f648d959671fb0a0142',
       }
     end
@@ -42,6 +43,7 @@ describe CreateDeploymentService, services: true do
       let(:params) do
         { environment: 'name with spaces',
           ref: 'master',
+          tag: false,
           sha: '97de212e80737a608d939f648d959671fb0a0142',
         }
       end