All-your-base: update version file (2.1.0 -> 2.3.0) and update one test (#1397)

exercises/all-your-base/.meta/version

-2.1.0
+2.3.0

exercises/all-your-base/src/test/java/BaseConverterTest.java

         expectedException.expect(IllegalArgumentException.class);
         expectedException.expectMessage("Bases must be at least 2.");
 
-        new BaseConverter(1, new int[]{});
+        new BaseConverter(1, new int[]{1});
     }
 
     @Ignore("Remove to run test")