Reworked README again to improve presentation
Merge pull request #82 from akleeman/new-readme

Reworked README again to improve presentation
Fix: dataset_repr was failing on empty datasets.
Added a test for empty datasets repr
Merge pull request #84 from akleeman/empty-to-str

Fix: dataset_repr was failing on empty datasets.
Scipy and NetCDF4 backend stores were improperly handling 0d vars.
Changed NetCDF3 string check to match that used in open_dataset.
Merge pull request #86 from akleeman/zerodim

BUG: Zero dimensional variables couldn't be written to file or serialized.
Rename DatasetArray.focus to DatasetArray.name

This is not mere bikeshedding -- "name" much more clearly implies the meaning
of this attribute and the fact that it should be a string. I think it makes
complete sense that array.name is the name with which the variable is associated
in the attached dataset.

"Focus" is ambiguous, and is a left-over from when I called DatasetArray
"DataView".

For an additional level of security (to protect users from themselves), I
have also hidden DatasetArray.dataset and DatasetArray.name behind properties
so they cannot be modified in-place (I can't think of any case in which this
would make sense instead of creating a new DatasetArray).

Note: For obvious reasons, this change will conflict with most of the current
pull-request.
Rename DatasetArray to DataArray

Per discussion in issue #85.
Fixed a few more references to "dataset array"

Also made the DataArray.name property give an informative error message when
you try to set it.
Fixed url in setup.py
Merge pull request #73 from akleeman/rename-focus-to-name

ENH: Rename DatasetArray.focus to DatasetArray.name
Dataset.reindex_like and DatasetArray.reindex_like

This provides an interface for re-indexing a dataset or dataset array using
the coordinates from another object. Missing values along any coordinate are
replaced by `NaN`.

This method is directly based on the pandas method `DataFrame.reindex_like`
(and the related series and panel variants). Eventually, I would like to build
upon this functionality to add a `join` method to `xray.align` with the
possible values `{'outer', 'inner', 'left', 'right'}`, just like
`DataFrame.align`.

This PR depends on PR #71, since I use its improved `copy` method for
datasets.
Refactored Dataset.reindex and generalized xray.align

The new xray.align can handle an arbitrary number of arguments, as well as
four different join options copied from `pandas.DataFrame.align` ('inner',
'outer', 'left' and 'right').

This gives us most of what we need to flip a switch and start automatically
aligning dataset arrays when they are used in mathematical operations. We'll
need to decide if we want to default to outer joins (like pandas) or inner
joins (which are less likely to blow up due to lack of memory or CPU).
Complete rebase on DatasetArray->DataArray
Dataset.from_dataframe and DataArray.from_series

Added new methods for creating Datasets and DatasetArrays from pandas objects.
Adjusted README to note that we require Python 2.7

Also adjusted setup.py slightly.
Merge pull request #89 from akleeman/readme-tweak

Adjusted README to note that we require Python 2.7
BUG FIX: CoordXArrays reduce to XArrays