Add cycle detection to the encoder (#33)

* Move Future Work items from README to TODO.md

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Add cycle detection to the encoder

Thread a seen-pointer set through encoding functions so that
self-referential pointers and maps are detected and returned as
errors instead of causing a stack overflow.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Remove Limitations section from README

Circular values are now detected and reported as errors, so the
limitation no longer applies.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Silvio <silvio@MBA13.home>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Add EncodeToStringWith and EncodeToValuesWith convenience functions (#16

)

Add parameterized versions of EncodeToString and EncodeToValues that
accept custom delimiter, escape, and keepZeros options. The original
functions now delegate to these new variants with default settings.

Add multi-version Go testing to CI (#31)

Add multi-version Go testing to CI (#31)

Fix golint import path (#17)

Merge pull request #12 from ajg/zeroes

Implement KeepZeros (Issue #11), Fix Test Formatting & Documentation