Allow whitelisted values in bower.json file created by bower init

A change in the behavior of `mout.lang.isEmpty()` in Mout v0.10.0
introduced a bug in `bower init`, preventing it from including Boolean
values in "bower.json".

This commit explicitly whitelists the types that are used in the
bower.json spec - Object, Array, String, Boolean - as well as Number for
future compatibility.

lib/commands/init.js

@@ -58,7 +58,7 @@ function readJson(project, logger) {
 function saveJson(project, logger, json) {
     // Cleanup empty props (null values, empty strings, objects and arrays)
     mout.object.forOwn(json, function (value, key) {
-        if (value == null || mout.lang.isEmpty(value)) {
+        if (!validConfigValue(value)) {
             delete json[key];
         }
     });
@@ -81,6 +81,18 @@ function saveJson(project, logger, json) {
     });
 }
 
+// Test if value is of a type supported by bower.json[0] - Object, Array, String, Boolean - or a Number
+// [0]: https://github.com/bower/bower.json-spec
+function validConfigValue(val) {
+    return (
+        mout.lang.isObject(val)  ||
+        mout.lang.isArray(val)   ||
+        mout.lang.isString(val)  ||
+        mout.lang.isBoolean(val) ||
+        mout.lang.isNumber(val)
+    );
+}
+
 function setDefaults(config, json) {
     var name;
     var promise = Q.resolve();

test/commands/init.js

@@ -49,7 +49,8 @@ describe('bower init', function () {
                 description: 'test-description',
                 moduleType: 'test-moduleType',
                 keywords: [ 'test-keyword' ],
-                license: 'test-license'
+                license: 'test-license',
+                private: true
             });
         });
     });