akleeman/xray — pull request #99 by shoyer (2014-04-11 08:14:13+00:00)
Title: Cleaned up Dataset indexing and groupby

Changes of note:

- Indexing a Dataset with an integer no longer drops 0-dimensional variables.
They are kept around as scalar values (without dimensions). This let me
remove at least one nasty hack.
- Restructured the internals of groupby and DataArray.concat (fixing #81).
- Removed support for grouping XArray objects since they will no longer be
in the public API.
- Added an apply method to DatasetGroupBy.