Update readme to point to published article and notebook viewer

README.markdown

@@ -1,10 +1,22 @@
-# psas-magnetometer-calibration
+# PSAS Magnetometer Calibration
 
 Example of how to do soft and hard iron calibration from a 3DOF magnetometer.
 
-### Install and run locally:
+**https://natronics.org/2019/magnetometer_calibration/**
+
+
+## Data
+
+Calibration and launch data is in the `data` directory.
+
+### Install code and run locally:
 
     $ pipenv install
     $ pipenv run jupyter notebook
 
-And edit the notebook.
+This should open a browser tap with the homepage of jupyter notebooks. Click on the `post.ipynb`
+file.
+
+You can also use an online notebook viewer pointed at the file, like this:
+
+https://nbviewer.jupyter.org/urls/git.natronics.org/natronics/psas-magnetometer-calibration/raw/branch/master/post.ipynb