Don't start the y axis always with zero

lib/widgets/weight/charts.dart

@@ -42,6 +42,9 @@ class WeightChartWidget extends StatelessWidget {
         )
       ],
       defaultRenderer: new charts.LineRendererConfig(includePoints: true),
+      primaryMeasureAxis: new charts.NumericAxisSpec(
+        tickProviderSpec: new charts.BasicNumericTickProviderSpec(zeroBound: false),
+      ),
     );
   }
 }

lib/widgets/workouts/charts.dart

@@ -50,6 +50,9 @@ class LogChartWidget extends StatelessWidget {
           );
         }),
       ],
+      primaryMeasureAxis: new charts.NumericAxisSpec(
+        tickProviderSpec: new charts.BasicNumericTickProviderSpec(zeroBound: false),
+      ),
       //behaviors: [new charts.SeriesLegend()],
     );
   }