Reworked show_tasks_by_priority() and speak_task()

Reworked: `show_tasks_by_priority()`, `speak_task()` and `self.lang_list`

Also opened an issue on `speak_task()` when starting task id != 1.
Merge pull request #6 from cclauss/patch-4

Reworked show_tasks_by_priority() and speak_task()