v2.4.0.rc1

• Added PQL support with pql() method (PR #201, fixes #167)
• Added ability to specify additional queries when using Node.facts() (#127)
• Improve the documentation (even more ;)) (PR #206, fixes #143 and #129)
• Fixed creating Edge objects (#202)
• Python 3.9 added as a supported version (#203)

This is a pre-release because of the big amount of changes in #201 that require more testing before a final release. Please feel free to test it in your projects!