FinQuant v0.2.3 (bugfix release)

This release is mainly a bugfix release, while it is also a resurrection of FinQuant.

Issues that have been resolved:

• Errors due to deprecated Pandas methods being used #73 #75
• Errors due to incorrect checks for float and int #74 #78
• Errors due to deprecated Numpy method being used #72 #79
• Minor change to structure of code: Stock was moved out of portfolio.py #80
• Tests have been updated #81
• Travis-CI was replaced with GitHub Actions for automated testing #82
• A list of contributors was added #85
• Documentation build was fixed #87 #88 #89

Special thanks to @PietropaoloFrisoni for reaching out and getting involved in the project.