Fixed some bugs with admin links on microlesson screen.
Cleaned up Alphabet units, put audio back in, added typing guide.
Lesson screen with progress indicators, basic answer checking on translate_word exercise.
Updates to lessons and tasks:

* Added boilerplate code for sample tasks (both javascript and underscore template).
* Translate_word task adapts state based on how incorrect your answer was.
* Deleted old, empty tasks, which will be replaced by tasks built off the boilerplate code.
New task for typing greek. Microlesson pulls from task sequence.
Super simple task for identifying letters of the alphabet.
Updates to admin, database updates.
Merge pull request #54 from OpenPhilology/development

Greater support for different kinds of tasks within a sequence.