provides a utility for tests to delete a path
addressed review comments

* does not fail if the test/temp/extensions directory does not exist
* reject promise in other failure cases for SpecRunnerUtils.remove
* added description of timeout case for requesting the temp filesystem
* checks for existence of main.js file
add node_modules used in testing
Ignore node_modules inside the test folder when running jshint
Merge pull request #3198 from adobe/dangoor/testing-domain

Enable installation tests