Switch from java.time.Instant to org.joda.time.Instant

[jisantuc]

Overview

joda.time.Instant.parse successfully parses a much wider range of valid ISO8601 timestamp formats (including +00 and -00 for time zone indications -- what even produces those? Clocks were a mistake).

Checklist

• New tests have been added or existing tests have been modified
• Changelog updated

Notes

The seemingly too specific decoder is the way it is because of the consistency law -- with emapTry, the exceptions weren't evaluating as equal, so the test kept failing.

Closes #150

[notthatbreezy]

This looks good. One suggestion though, add some tests that cover a few examples of formats that stac4s can now parse, but previously could not.