Version 2.4.1. Faster shapefile writes.

What's Changed

• Add speed_test.py and .yml by @JamesParrott in #336
• Add Writer speed tests by @JamesParrott in #338
• Combine f.write(pack( "<d"etc., )) calls by @JamesParrott in #341

Full Changelog: 2.4.0...2.4.1