Fix travis tests as per discussion

- Use cache to speed up apt installation
- Install apache2 due to internal PHP webserver routing issues
- Use 1 level of git to speed up git clone and lower bandwidth for
drupal.org
Use getId() method instead of id in Drupal\Core\Language\Language as for #2340667
Merge pull request #103 from pcambra/2340667_id_getid

Use getId() method instead of id in Drupal\Core\Language\Language
Merge pull request #102 from joshuataylor/travis-fix-tests

Fix travis tests as per discussion