Update README for tutorials directory.

Author: frreiss

tutorials/README.md

@@ -1,4 +1,16 @@
 # Detailed Tutorials for Text Extensions for Pandas
 
-This portion of the project is still a work in progress.
+This area of the Text Extensions for Pandas source code contains detailed
+end-to-end examples, broken down into multiple Jupyter notebooks.  Each use
+case occupies a separate subdirectory of the `tutorials` directory.
+
+To run any of these tutorials, check out a copy of the Text Extensions for
+Pandas source tree, follow the instructions in the main `README.md` file to
+create a JupyterLab environment, and run the notebooks in the directory you're
+interested in.
+
+Subdirectories:
+* `corpus`: Model training and analysis code used in the CoNLL-2020 paper ["Identifying Incorrect Labels in the CoNLL-2003 Corpus"](https://www.aclweb.org/anthology/2020.conll-1.16/).
+* `market`: Market intelligence use case involving mining the names and
+  titles of executives from IBM press releases.