Feature/notebooks (#5)

* feat: add notebook on elementary risk models

* feat: add notebook on multi-factor models

* feat: add notebook on sector models

* fix: add references to notebooks

* fix: add references to sector model notebook, update README.md

README.md

@@ -3,5 +3,9 @@
 Risk attribution and optimisation using a multi-factor equity risk model.
 
 Includes functionality to:
-* Calculate risk, marginal risk contributions and risk concentration measures
+* Calculate risk, risk contributions and risk concentration measures
 * Optimise a portfolio to be factor *neutral* or *tolerant*
+
+The directory `notebooks` contains some jupyter notebooks which provide a 
+starting point to exploring and developing equity risk models. It is by no 
+means comprehensive, so the usual caveats apply.