Reworked the tests, read more

I've brought the tests up to scratch, except for compounds im the
parser, because I'm too damn tired to do that over SSH. It looks like
collections are right-recursive, whixh was unintended but still works
just fine.

I've also added the '--verbose' flag to the repl to control the
debugging output.

Several obscure bugs have been fixed, and comments have been tweaked.

Mustfail tests are still needed, but that's a low priority. See #142.

Fixed #151

tests/integrations/test_variables.toy

@@ -50,7 +50,7 @@ print !true; //false
 print !false; //true
 
 //precedence
-print true && false || true; //TODO: a warning is needed for this
+print true && false || true; //TODO: a grouping warning is needed for this
 
 //types
 var a: int;
@@ -67,4 +67,9 @@ var c: int const = 42;
 
 print c;
 
+//indexing
+var s = "Hello" .. "world!";
+
+print s[3, 3];
+
 //TODO: type casting