Yaml, more features

This PR adds support for more yaml types. To make the tests pass, it needs the fixed version of timestamp>rfc3339 from 622f333, but as discussed in https://github.com/slavapestov/factor/pull/1057 622f333 is just a proof of concept and is not meant to be merged in.

I can also modify the failing test to not use decimals and remove 622f333 if that's better ?
Since this doesn't work with timestamps like ``1/3``, but should work with most ratios (and *could* sorta work with ``1/3``), why not just inline the portion you care about from ``decimals`` (so we don't have an extra dependency?):

```factor
second>> dup ratio? [
    "." write 1 mod number>string write
] [ drop ] if 
```