[#2] Added TagType
[#2] Added RecipeTag model
[#2] RecipeTag stores tag as lowercase
[#2] RecipeTag repr and unicode
[#2] RecipeTag will display the added_by user, or 'System' if no user, with the 'who_added' function
[#2] tests for RecipeTag init
[#2] tests for RecipeTag unicode and repr
[#2] admin for RecipeTag; added clean method to handle case-insensitive validation in admin/model forms
[#2] tests for RecipeTag.clean
Slug on recipe gets updated to match title
[#2] tests for RecipeTag.save
[#2] fix for Django's auto_now_add not actually creating a default
[#2] fixture for some default tags
[closes #2] Updated README to mention recipe_tags fixture