Allow setting ymin in likelihood scan plot

quickstats/plots/likelihood_1D_plot.py

@@ -52,7 +52,7 @@ class Likelihood1DPlot(AbstractPlot):
     
     def draw(self, xattrib:str='mu', yattrib:str='qmu', xlabel:Optional[str]=None, 
              ylabel:Optional[str]="$-2\Delta ln(L)$",
-             ymax:float=7, xmin:Optional[float]=None, xmax:Optional[float]=None,
+             ymin:float=0, ymax:float=7, xmin:Optional[float]=None, xmax:Optional[float]=None,
              draw_sigma_line:bool=True, draw_sm_line:bool=False):
         ax = self.draw_frame()
         if isinstance(self.data_map, pd.DataFrame):
@@ -109,7 +109,7 @@ class Likelihood1DPlot(AbstractPlot):
             
         handles, labels = self.get_legend_handles_labels()
         ax.legend(handles, labels, **self.styles['legend'])
-        ax.set_ylim([0, ymax])
+        ax.set_ylim([ymin, ymax])
         ax.set_xlim([xmin, xmax])
 
         self.draw_axis_components(ax, xlabel=xlabel, ylabel=ylabel)