Merge pull request #17 from udacity/development

Emergency fix - skip user profile sync if there is no active user
Merge pull request #19 from udacity/development

Merged with updates from upstream
Merge pull request #21 from udacity/development

Merged with updates from upstream
Merge pull request #23 from udacity/development

Merged development
Merge pull request #26 from udacity/development

Merged with updates from upstream
Merge pull request #28 from udacity/development

Merge latest changes from upstream.
Merge pull request #30 from udacity/development

Adding subcategories and API for pulling topics tagged with a subcategory.
Merge pull request #34 from udacity/development

Merged with updates from upstream
Merge pull request #36 from udacity/development

Merged with updates from upstream
feat(skin): add custom udacity skin
Merge branch 'development' into udacity_skin--attila
feat(skin): add email during registration
Merge pull request #38 from cdman/udacity_skin--attila

feat(skin): add custom udacity skin