Added doctest for getting group keys.
Merge pull request #25 from mcflugen/fix-unit-tests

Fix unit tests
Merge pull request #26 from mcflugen/fix-unit-tests

Moved test script so unit tests won't find it.
Mainly component docstrings

* Expanded docstrings in my components.
* Added a new diffusion driver.
* Tweaked functionality of diffusion/diffusion, Perron_nl_diffuse,
route_flow_dn, & fastscape_stream_power.
* Added some BC return properties to base.py.
* Began component tutorial.
Changed theme to default, turned off autosummary.
Cleanup up model_grid.rst
Added documentation.

Added
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* Added lots of new examplesand doctests.
* Fomatted for numpydoc.

Changed
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* Methods that take ids as arguments should be able to accept a scalar,
  array-like, or nothing to indicate a single id, a set of ids, or all
  ids, respectively. Going through and updating this where possible.
Changed decorators to use functools.wraps.
Added more documentation and doctests.
Changed unit_test to _unit_test.
Testing new doc

Test upload of new doc for component tutorial; it’s not compiling for
me locally.
Bulked out tutorial on component coupling

Drastically improved content of tutorial on coupling. Still feels very
wordy/dry though. Maybe add more images? Think content is good though.
Typo
Updated rst files with sphinx-apidoc.
Updated rst doc files with sphinx-apidoc.
Typo in landlab_component_tutorial
Apparently, a necessary recommit of new rst file?
Improved look of coupled tutorial, & typos

Included pics, mended some formatting & typo issues w coupled tutorial
(& fastscape_stream_power)
Doc tweaks

Documentation tweaks per discussions in LL annual meeting.
More doc tweaks