#110 add kwarg to nearest_cell for indexing

[debboutr]

Here's an attempt at adding the functionality of the nearest_cell method to allow the user to define another approach to how the pour point geometry will be indexed in the raster. I'd be happy to add a test, but I am unsure of how you are running tests right now. Is there a testing package that you are using? Thanks

[coveralls]

Pull Request Test Coverage Report for Build 279

• 7 of 7 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.007%) to 81.434%

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Totals
Change from base Build 272:	0.007%
Covered Lines:	2022
Relevant Lines:	2483

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💛 - Coveralls

[mdbartos]

Thanks for the PR. To add tests, add a new function to /tests/test_grid.py that checks the new functionality. The new function will be called automatically by pytest.

You can run tests locally by navigating to the root directory of the repo and running:

pytest

To run tests + coverage check, run:

pytest --cov=pysheds/

For more info, see: https://docs.pytest.org/en/latest/

Note that pushing to your fork will automatically trigger the test on Travis.

[debboutr]

Just popped a test in that I think provides some coverage for this feature. Any feedback towards improvement would be appreciated. One thing I noticed when trying to run pytest was that you can't have pyproj installed from `conda or you will get this error

installing w/ pip did the trick for me though. I got the tests to pass, but not with the --cov flag, not sure what to do there, sorry. It says unrecognized arguments, is there another package that I need to do that?

Thanks!