#Create a telephone directory

Allow a users to enter the First Name, Last Name, Cell Phone Provider and Cell Phone number of a contact. Add support for deleting contacts.

Add a filter function that allows one to filter the data in the telephone directory. The function should take a filter function as a parameter that allows one to filter the entries in the telephone directory.

Support the following type of filters:

• Find all the users with the same first name.
• Find all the users with the same surname.
• Find a users phone number.
• Find all the users that use the same Cell Phone Providers
• Find how many contacts there are for each Cell Phone provider.

Create this using TDD.

Once done with the above create a User Interface for this.