v2.1.0
  - re-wrote as.yaml in C (using libyaml's emitter)
  - removed the `pre.indent` option to as.yaml, mainly because libyaml
    doesn't support pre-indention and I'm not sure the option is useful
    anymore; will revisit if requested

v2.0.0
  - switch from the Syck parser to the libyaml (0.1.4) parser
  - changed behavior:
    - sequences of sequences no longer collapse when they contain the same
      type; ex: yaml.load("[1, [2, 3], 4]") returns list(1L, c(2L, 3L), 4L)

v1.2.0
  - added support for loading R expressions (using the !expr tag)
  - added multiline string support
  - added support for nameless lists in as.yaml (converts to a sequence)

v1.1.0
  - added support for omaps
  - added yaml.load_file function to read from files/connections
  - using format instead of as.character now in as.yaml.default

v1.0.2
  - fixed as.yaml bug where a nested empty list wasn't converted correctly

v1.0.1
  - yaml.load will now load empty documents (bug submitted by Jeff Klingner)
  - as.yaml will return '[]' for empty objects (patch submitted by Brendan O'Connor)
  - as.yaml will now create valid YAML for a list that contains a list of length
    one (bug submitted by Gabor Grothendieck)
