v0.4.0

• Many improvements and new features for RoundtripAst.
  • Improved support for replacing keys and values. There is experimental
    support for replacing dicts and lists, and now full support for all other
    data types.
  • Added option enforce_types, which provides experimental support for
    replacing keys and values with objects of a different data types.
  • Added support for custom encoders.
  • Added preliminary support for __getitem__-style access (for example,
    ast['key'].value).
  • Added access to trailing comments (not doc comments) with new node
    attributes key_trailing_comment, value_trailing_comment,
    value_start_trailing_comment, and value_end_trailing_comment. These
    also allow modification of existing trailing comments.
• New loading options: custom_types allows use of custom data types.
  empty_default is a function that is called to produce a
  default value when there is no data to load.
• New dumping options that control output appearance, data types, and data
  structures: aliases, circular_references, integers,
  only_ascii_unquoted, only_ascii_source, extended_types,
  python_types, baseclass, trailing_commas, compact_inline,
  inline_depth, nesting_indent, start_list_item, and
  flush_start_list_item.
• Fixed bug with round-tripping bools.
• Fixed bug in error reporting for reserved words like inf in key paths.