Use absolute URLs for fixtures

Former-commit-id: b71d587d

spec/javascripts/test_bundle.js

 // enable test fixtures
 require('jasmine-jquery');
-jasmine.getFixtures().fixturesPath = 'base/spec/javascripts/fixtures';
-jasmine.getJSONFixtures().fixturesPath = 'base/spec/javascripts/fixtures';
+jasmine.getFixtures().fixturesPath = '/base/spec/javascripts/fixtures';
+jasmine.getJSONFixtures().fixturesPath = '/base/spec/javascripts/fixtures';
 // include common libraries
 require('~/commons/index.js');