Add basic spinach tests for project builds

features/project/builds.feature

+Feature: Project Builds
+  Background:
+    Given I sign in as a user
+    And I own a project
+    And CI is enabled
+    And I have recent build for my project
+
+  Scenario: I browse build summary page
+    When I visit recent build summary page
+    Then I see summary for build
+    And I see build trace

features/steps/project/builds.rb

+class Spinach::Features::ProjectBuilds < Spinach::FeatureSteps
+  include SharedAuthentication
+  include SharedProject
+  include SharedBuilds
+  include RepoHelpers
+
+  step 'I see summary for build' do
+    expect(page).to have_content "Build ##{@build.id}"
+  end
+
+  step 'I see build trace' do
+    expect(page).to have_css '#build-trace'
+  end
+end

features/steps/shared/builds.rb

+module SharedBuilds
+  include Spinach::DSL
+
+  step 'CI is enabled' do
+    @project.enable_ci
+  end
+
+  step 'I have recent build for my project' do
+    ci_commit = create :ci_commit, project: @project, sha: sample_commit.id
+    @build = create :ci_build, commit: ci_commit
+  end
+
+  step 'I visit recent build summary page' do
+    visit namespace_project_build_path(@project.namespace, @project, @build)
+  end
+end