demo/json.should: we should be able to test elements in nested lists

Reworked from examples by @flothoni.
See #54.

demo/json.should

@@ -13,6 +13,8 @@ j:concepts.directions
 j:concepts.wuxing.earth
 j0:concepts.winds   
 j:numbers[3].meaning
+j:numbers[4][0]
+j0:numbers[4][4]
 j0:numbers[0].meaning
 j0:numbers[42].meaning
   
@@ -28,6 +30,7 @@ j:concepts.directions:rth
 j:concepts.directions[0]:rth
 j0:concepts.directions[3]:rth
 j0:concepts.wuxing:st
+j:numbers[4][1]:0.8
 
 $ The number of matching expressions can also be tested
 j2:concepts.directions:st    
@@ -42,5 +45,3 @@ jr>1:concepts.directions:e.*?st
 $ Data that are not parsed as json yield 0 occurrences
 echo "hello, world"
 j0:hello
-
-

demo/tests/concepts.json

 {
-  "numbers" : [ 3, 7, 12, {"meaning": 42} ],
+  "numbers" : [ 3, 7, 12, {"meaning": 42}, [0, 0.8] ],
 
   "concepts":
   {