Emoji extractor improvement
Created by: ztenma
Migrates emoji-extractor script to Python3, improving code style (PEP8, etc). Adapts work done by ariasuni in PR #575.
Tested against both Python 3.6 (latest stable 3.X) and 3.4 (earliest stable 3.X) by running on NotoColorEmoji.ttf from googlei18n/noto-emoji.