Clean up and standardize function help blurbs

[unicornsasfuel]

Not all the functions in cryptanalib have help blurbs. Let's document all the functions and their expected return values and whatnot like so:

"""
Get integer nth roots.

:param x: The number to get the integer root of.
:param n: The root we want (e.g. 3 for cube root).
:return: The nth root of x rounded to an integer.
:rtype: long
"""

[q2dg]

Well, it seems this project is abandoned, unfortunately

[unicornsasfuel]

@q2dg While this project is abandoned, I (the original author) am maintaining a Python3-compatible fork of the cryptanalib module at https://github.com/unicornsasfuel/cryptanalib3. The FeatherDuster interface has not yet been recreated in Python3.