Update attribution #350 by adding NOTICE.txt file

[C-Lion]

Overview

I see the current Apache license document & I assume you didn't mean to alter that.

Proposed Changes

I followed the advice on the post linked below & created a new NOTICE.txt file for your attribution information. Let me know if you want anything else added to this document or if you had something else in mind & I'll be happy to correct it per your requests. https://opensource.stackexchange.com/questions/2312/how-should-you-put-attribution-into-your-project