Implement encoder interface (partially)
Add `filename` to `Pos`, replace `Token` -> `Pos` in `Node`
Return back tocken tracking in parser
Ast creation sketch
Ast-based json conversion implemented
Added two json tests for map merging
Partial implementation of Decoder
Add first decoder test
First version of working decoder
Implement AnyJson wrapper
Implement emitting code for Ast
Made YamlDecoder::new public
Implemented very minimal validation support
Minimal high level interface added
Implement decoding sequences and mappings
Tag parsing for scalars implemented
Add Mapping validator
Implement Sequence validator
Allow dashes instead of underscores in struct members
Made validator struct members public