convert ReproSchema2RedCap from js to py

[yibeichan]

this is a sister pr of #30 ; here I converted reproSchema2RedCap.js to reproschema2redcap

changes include:

• fully converted python file reproschema2redcap.py (have tested it manually—successfully converted a reproschema protocol to a redcap csv)
• integrated the function to cli.py
• updated README.md for the instruction: use it as CLI and use it in python directly

at this point, the above changes should be enough. we can improve it later if needed.