When nesting for non-list contexts, inherit list info.

This ensures that if you enter a conditional block while inside a list
block, the list "state" from the outer list will still be visible. For
example (somewhat contrived, but gets the point across):

{{#list}}
{{#name}}{{-index}}. {{.}}{{/name}}
{{^name}}{{-index}}. No name!{{/name}}
{{/list}}

Yields something like:

1. Bob
2. Mary
3. No name!
4. Jim

Fixes #90.

src/main/java/com/samskivert/mustache/Mustache.java

@@ -878,7 +878,7 @@ public class Mustache
             } else if (_comp.isFalsey(value)) {
                 // omit the section
             } else {
-                executeSegs(tmpl, ctx.nest(value, 0, false, false), out);
+                executeSegs(tmpl, ctx.nest(value), out);
             }
         }
         @Override public void decompile (Delims delims, StringBuilder into) {

src/main/java/com/samskivert/mustache/Template.java

@@ -157,7 +157,7 @@ public class Template
                 execute(currentCtx, out);
             }
             @Override public void execute (Object context, Writer out) {
-                execute(currentCtx.nest(context, 0, false, false), out);
+                execute(currentCtx.nest(context), out);
             }
             @Override public Object context () {
                 return currentCtx.data;
@@ -339,6 +339,10 @@ public class Template
             this.onLast = onLast;
         }
 
+        public Context nest (Object data) {
+            return new Context(data, this, index, onFirst, onLast);
+        }
+
         public Context nest (Object data, int index, boolean onFirst, boolean onLast) {
             return new Context(data, this, index, onFirst, onLast);
         }