Added 0257_Binary_Tree_Paths.py

[matheusphalves]

IMPORTANT: Please do not create a Pull Request without an issue.

All Submissions:

• I have read the CONTRIBUTING document.
• My code is written in Python3 and is ending with .py
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• I have checked that my submission does pass the test on LeetCode.com
• Does your filename follow the naming Conventions?
• Have you linked your PR to an Issue?

Closing issues
Closes #500

[vJechsmayr]

Code does not pass the test on LeetCode

Please check again! 😸

[matheusphalves]

Done! Sorry! I forgot to add ' # ' on all lines of class TreeNode. Now, this solution works on LeetCode!
Runtime: 32 ms

[vJechsmayr]

Thanks for changing! Code works now 😸
Thanks for contributing - Merged!

Runtime: 32 ms

Happy Hacktoberfest!