* Change package requirements to python >= 3.9 and specifically exclude pp38 from wheel building
* Retain miniSEED "sequence number" if packing a parsed v2 record
* Change example codes in README.md for usability
* Set defaults for class MS3Record matching msr3_init(). Fixes 3
* Create comprehensive repr() for MS3Record and leave str() as a terse summary. Fixes 4
* Update libmseed to v3.1.3