unpinned versions of pandas (and scipy and numpy) (plotly#2278)

* unpinned versions of pandas (and scipy and numpy)

* deubg

* debug

* debug

Author: emmanuelle

Diff for: binder/requirements.txt

@@ -2,11 +2,11 @@ jupytext
 plotly==4.5.4
 jupyter
 notebook
-pandas==0.23.0
+pandas
 statsmodels==0.10.1
-scipy==1.3.1
+scipy
 patsy==0.5.1
-numpy==1.16.0
+numpy
 plotly-geo
 psutil
 requests

Diff for: contributing.md

@@ -8,7 +8,7 @@ Check out the [Code of Conduct](CODE_OF_CONDUCT.md). Don't tl:dr; it, but the ge
 
 ## Have a Bug Report?
 
-Open an issue! Go to https://github.com/plotly/plotly.py/issues. It's possible that your issue was already addressed. If it wasn't, open it. We also accept PRs; take a look at the steps below for instructions on how to do this.
+Open an issue! Go to https://github.com/plotly/plotly.py/issues. It's possible that your issue was already addressed. If it wasn't, open it. We also accept PRs; take a look at the steps below for instructions on how to do this. 
 
 ## Have Questions about Plotly?