Date/Day/Month Update

Adds Date/Day/Month Functionality.
Day & Month are enums. Day has a numerical value associated with each
option.
Date contains a Month, Day, and Year (int) and can check to see if the
month/day combination is valid. Also has getters for all three values.
User Update

Completed all of the User methods.
Turned Validity into a stand-alone enum.
Link Update

Filled in Link methods.
Added UninitializedObjectException Class