Big clean up and install instructions

[Roald87]

I changed a lot of things, maybe you're interested in them:

• formatted the python code with black
• organized the imports
• added nltk package downloads
• added a conda.yml and requirements.txt + install instructions
• changed some code that gets rid of extra spaces around keywords (although this did seem to impact the scores a little and a lot for the general skills)
• some variable renaming here and there
• finally, added some hard and soft skills