Enables title and subtitle configuration through Frontmatter.
Adds dropdown menu to expose available courses list.
Merge branch 'master' of github.com:redu/courses-starter-kit

Conflicts:
	source/_header.html.erb
	source/index.html.erb
Adds content of Scrum course.
Enables directory_indexes and adds courses urls to nav dropdown.
Fixes TDD course informations.