Add minimum Python version to README

README.md

@@ -7,6 +7,8 @@ of dividing the inverse odds by the booksum [[3](#3)].
 
 # Installation
 
+Requires Python 3.5 or above.
+
 ```
 pip install shin
 ```
@@ -52,4 +54,4 @@ Market for State-Contingent Claims”. The Economic Journal,
 <a id="1">[3]</a>
 [E. Štrumbelj, "On determining probability forecasts from betting odds".
 International Journal of Forecasting, 2014, Volume 30, Issue 4,
-pp. 934-943.](https://doi.org/10.1016/j.ijforecast.2014.02.008)
+pp. 934-943.](https://doi.org/10.1016/j.ijforecast.2014.02.008)