Removed create_tine and update_time fields.
These fields are going to be populated automatically.
Enhanced the display of post with a certain tag.
Overriden the behaviour of beforeSave, afterSave and afterFind methods.

Refactore the rules method.
Modified the actionIndex method. Also loadModel method received some modifications.
Added three methods inside Tag class.
updateFrequency, addTags, removeTags.