Replace format the license to use markdown

COPYING has been replaced with LICENSE.md, but the terms of the license
remain unchanged; only the formatting has changed.
Move README.markdown to README.md
Update Python Problem 36 and euler.palindromic

Added is_binary_palindromic to check if a number's binary representation
is palindromic.
Support for negative numbers in euler.palindromic

All numbers now have their absolue value taken, and this result is
checked instead. This removes issues of having minus signs in the
number.