Merge branch 'master' into population

Author: dsargent

covid_xprize/examples/predictors/linear/Example-Train-Linear-Rollout-Model.ipynb

@@ -221,7 +221,7 @@
     "        # Flatten all input data so it fits Lasso input format.\n",
     "        X_sample = np.concatenate([X_cases.flatten(),\n",
     "                                   X_npis.flatten()])\n",
-    "        y_sample = all_case_data[d + 1]\n",
+    "        y_sample = all_case_data[d]\n",
     "        X_samples.append(X_sample)\n",
     "        y_samples.append(y_sample)\n",
     "\n",