rename stops to stay_locations in preprocessing.detection

[vlingenfelter]

In response to issue #14: renamed stops to stay locations in the preprocessing.detection to be more in line with the literature/language used in Toyama 2004.

[michelegirolami]

Dear @vlingenfelter thanks for your PR. I checked it and I found the following issues to be also fixed:

• some unit tests do not succeed. In particular, it is required to update those tests still using the obsolete detection.stops() instead of detection.stay_locations(). I found these tests: skmob/core/tests/test_trajectorydataframe.py, skmob/models/tests/test_epr.py, skmob/preprocessing/tests/test_detection.py, skmob/utils/tests/test_plots.py
• the documentation generated with sphinx also requires to be updated. As for example, the class trajectorydataframe.py refers some old detection.stay_locations() code snippets
• the unit test named test_detection.test_stops() requires to be renamed to test_stay_locations()

I can help you on this, if you grant me commit permissions to your PR so that I directly update PR #206. We would like to include this PR in the next release, therefore (if possible ) let me know how speed up the process. Thanks again!

[michelegirolami]

Hi @vlingenfelter I just checked that you already allowed your PR for external contribution. I added some more staff fixing the rename of the method stops() . Check it out

@gbarlacchi this PR points to the master branch, we should direct it to branch 1.2.x, is this correct?