Fix plot links

README.md

@@ -40,7 +40,7 @@ We cut out everything outside of the mask with `zipmask_pack()`:
 s = zipmask_pack(m, mask);
 plot_lattice3D(s.data, s.mask, 'compressed matrix/mesh');
 ```
-![plot1](doc/plot1.png)
+![plot1](doc/plot2.png)
 
 
 And re-grow the small data with `zipmask_unpack()`:
@@ -49,7 +49,7 @@ And re-grow the small data with `zipmask_unpack()`:
 [um, umask] = zipmask_unpack(s);
 plot_lattice3D(um, umask, 'expanded matrix/mesh');
 ```
-![plot1](doc/plot1.png)
+![plot1](doc/plot3.png)
 
 
 # Limitations