Add decorator to easily specify number of arguments

[Guilherme-Vasconcelos]

Describe your idea
Instead of manually checking number of arguments in each function, add a decorator.

@num_args(0)
@authorize
def start(...):
    ...

Extra information
There are some edge cases:

• Some functions require any number of arguments
• However, some functions can accept a variable number of arguments but require a minimum (such as remindme, which requires at least 3)
• Suggestion:
  • Omitting @num_args means any number of arguments
  • @num_args(X) means exactly X arguments
  • @min_num_args(X) means at least X arguments
  • @max_num_args(X) means at most X arguments