Update pandas-summary dependency

Previously the structured data analysis notebook (course 1, lesson 3) would
fail on the DataFrameSummary command due to there being a change in how Pandas
handled types and pandas-summary. There is a change in pandas-summary, but the
version that released it seems to have gone down [1], so conda doesn't know how
to install it. So we have to hardcode it to the newly released version until
the version changes.

[1]: polyaxon/traceml#14

environment.yml

@@ -96,7 +96,7 @@ dependencies:
   - torchvision>=0.1.9
   - opencv-python
   - isoweek
-  - pandas_summary
+  - pandas_summary==0.0.5
   - torchtext
   - graphviz
   - sklearn_pandas