static/app.js is not encoded as utf-8 when loaded

In app.py line 53 `app_js = open("static/app.js")` is not loaded with utf-8 encoding resulting in the hasher in line 54 complaining:

> UnicodeDecodeError: 'charmap' codec can't decode byte 0x8f in position 9125: character maps to \

I solved it by adding the encoding: ` app_js = open("static/app.js", encoding='utf-8')`