add_basemap: keep original axis limits of figure

[jorisvandenbossche]

Opening this for discussion: in my original implementation (http://geopandas.readthedocs.io/en/latest/gallery/plotting_basemap_background.html#contextily-helper-function) I reset the axis limits to the original ones when the ax is passed to the function.

One reason to do this: the extent of the figure does not depend on the zoom level (on how many tiles are merged).

Closes https://github.com/darribas/contextily/issues/45

[coveralls]

Coverage increased (+0.04%) to 90.535% when pulling d7cb4c0 on jorisvandenbossche:add_basemap-restore-axis into cb7a4a0 on darribas:master.

[darribas]

Nice! so, just to make sure I get it correctly, this PR will make sure the extent of the plot will stay that of the original plot, not that of the pulled down full image, right?

[jorisvandenbossche]

Yes, that is correct

[jorisvandenbossche]

(will add a test if you approve the change)

[darribas]

Yes, I think this makes sense. Quick question, would this also apply to the case where url is a local file?

[jorisvandenbossche]

Updated the PR to fix merge conflicts.

Yes, I think this makes sense. Quick question, would this also apply to the case where url is a local file?

For now, I didn't make any distinction between both.

And I also updated the test

[darribas]

Cool. One more thing, could you please add the option of reset_extent as mentioned in #45? I think you're right it makes more sense to set the default to True, but it I think in some contexts (particularly when url points to a local file), the user might be interested in letting the extent be reset by the addition.

[darribas]

I think giving the option should just be adding here:

if reset_extent:
     ax.axis(...)

[darribas]

@jorisvandenbossche I've cleaned conflicts in one of the tests with current master and added the option to reset the extent (as opposed of always doing it) into a PR to your branch. If you merge that one, I'm happy to merge this too into master.

[darribas]

Whoops, looks like this introduces errors on the tests now...

https://travis-ci.org/darribas/contextily/jobs/522345969

These are in addition to the 3.5 issue and come up in 3.6. Would you mind having a look into it @jorisvandenbossche?