Add a decorator for creating table via class-style.

[YogiLiu]

This feature add a decorator to create table via class-style, it's friendly to type hint.

from pypika import table_class, Table, Field, Query

@table_class('customers')
class Customer(Table):
    id = Field('id')
    first_name = Field('fname')
    last_name = Field('lname')
    phone = Field('phone')

q = Query.from_(Customer).select(Customer.id, Customer.first_name, Customer.last_name, Customer.phone)

The decorator's parameters are same as Table.__init__.