Timeago: libraries_get_path isn't a D8 function

Hi,

Library build and language uses, are gated behind a function_exists('libraries_get_path') which doesn't exist anymore in Drupal 8.

Same problem with the library detection in the requirement.

Two options in my opinion :
- Library path might be retreive with library.discovery. Something like this : $path = \Drupal::service('library.discovery')->getLibraryByName('drupal', 'timeago');
but library definition should be rework, as 3th party libraries are usually managed with composer
OR
- Path might be hardcoded as this path is expect to be fix (Already fix in README.txt). A crude file_exist() or better, might be use as trigger

Any opinions ?