v0.3

New features:

• Revamped coordinates: "coordinates" now refer to all arrays that are not
  used to index a dimension. Coordinates are intended to allow for keeping track
  of arrays of metadata that describe the grid on which the points in "variable"
  arrays lie. They are preserved (when unambiguous) even though mathematical
  operations.
• Dataset math xray.Dataset objects now support all arithmetic
  operations directly. Dataset-array operations map across all dataset
  variables; dataset-dataset operations act on each pair of variables with the
  same name.
• GroupBy math: This provides a convenient shortcut for normalizing by the
  average value of a group.
• The dataset __repr__ method has been entirely overhauled; dataset
  objects now show their values when printed.
• You can now index a dataset with a list of variables to return a new dataset:
  ds[['foo', 'bar']].

Backwards incompatible changes:

• Dataset.__eq__ and Dataset.__ne__ are now element-wise operations
  instead of comparing all values to obtain a single boolean. Use the method
  Dataset.equals instead.

Deprecations:

• Dataset.noncoords is deprecated: use Dataset.vars instead.
• Dataset.select_vars deprecated: index a Dataset with a list of
  variable names instead.
• DataArray.select_vars and DataArray.drop_vars deprecated: use
  DataArray.reset_coords instead.