Attempt to download course description.

Conflicts:
	coursera/coursera_dl.py

[rbrito: Fix conflicts and follow some of the modularization.]
Changed URL to maestro which returns JSON.

Conflicts:
	coursera/coursera_dl.py

[rbrito: Fix more conflicts due to modularization.]
Fixed list parameter, which somehow worked in Py2.7.
Fixed path to about.json to use class_name.
coursera: Fix PEP-8 issues.
coursera: define: Fix URL of information about courses.
coursera: Remove unused import.
coursera: Add debugging information.
coursera: Try to improve readability with 'with'.
coursera: Add more debugging information.
coursera: Avoid necessity of having a directory named after the class.

The directory is not necessarily present at that point and we should
probably create it as we do with the lectures and other resources.