Package JSON cleanly. minimongo test passes on IE7

packages/json/package.js

@@ -0,0 +1,9 @@
+Package.describe({
+  summary: "Provides JSON.stringify and JSON.parse for older browsers",
+  internal: true
+});
+
+// We need to figure out how to serve this file only to browsers that
+// don't have JSON.stringify (eg, IE7 and earlier -- or is that IE8?)
+
+Package.client_file('json2.js');

packages/livedata/package.js

@@ -3,6 +3,7 @@ Package.describe({
   internal: true
 });
 
+Package.require('json');
 Package.require('underscore');
 Package.require('session');
 Package.require('minimongo');

packages/minimongo/package.js

@@ -6,6 +6,7 @@ Package.describe({
 // It would be sort of nice if minimongo didn't depend on underscore,
 // so we could ship it separately.
 Package.require('underscore');
+Package.require('json');
 
 Package.client_file('minimongo.js');
 Package.client_file('selector.js');