Add dvc usage instructions to README.rst (#122)

Author: sadhana-r

README.rst

@@ -55,6 +55,37 @@ Dev mode
 
    pip install -e .[dev]
 
+Version control of database using DVC (Data Version Control)
+------------
+
+Data Version Control (DVC) is a data management tool that is meant to be run alongside Git.
+In this project DVC is used to link changes in the code to specific versions of the database. DVC can be
+used when this project is installed in Dev mode. You can read more about DVC and how to use it `here <https://dvc.org/doc/start>`_.
+Note: Remote storage of the database currently uses google drive storage that requires a "gdrive_client_secret"
+for user access authentication.
+
+DVC usage
+^^^^^^^^^
+
+To download the database:
+
+.. code:: sh
+
+   git pull
+   dvc pull # Requires access to remote storage
+
+This will download a directory 'db_dvc' in the repo directory that
+contains the corresponding version of database files.
+
+To commit updates to the database:
+
+.. code:: sh
+
+   dvc add db_dvc
+   git commit -m "Describe updates to database"
+   git push
+   dvc push #Requires access to remote storage
+
 Disclaimer
 ----------