0.2.0

New features:

• Add load_all()/dump_all() to support multi-document YAML.
  (@grahamgower, #239, #335)
• Add CLI.
  (@grahamgower, #339)
• Add to_ms() function.
  (@grahamgower, #74, #354)
• Allow for "Infinity" as start times for demes and migrations in input
  YAMLs and dicts.
  (@apragsdale, #358, #386)

Breaking changes:

• A pulse event now allows for simultaneous sources and takes arguments
  sources and proportions instead of source and proportion. The
  sources and proportions must be provided as a list, even when there is
  only a single source deme.
  (@apragsdale, #353)
• Disallow null values and blank entries in input YAML models.
  (@apragsdale, #340, #387)

Bug fixes:

• Fix various issues in from_ms() with -es/-ej commands.
  (@grahamgower, #350, #351, #352)
• Fix some pulse edge cases when pulse events occur at the same time.
  (@grahamgower, #328, #357, #362)
• todict_simplified() now properly handles symmetric migrations when the
  end times of the demes involved differ.
  (@apragsdale, #384, #385)