fixing issue #46 - .addQuery("empty") wonldn't add "?empty"

docs.html

@@ -545,6 +545,9 @@ <h3 id="search-add">addSearch(), addQuery()</h3>
 uri.addSearch({ foo: "bar", goodbye : ["world", "mars"] });
 // uri == "?hello=world&amp;hello=mars&amp;foo=bar&amp;goodbye=world&amp;goodbye=mars"
 
+uri.addSearch("no-value");
+// uri == "?hello=world&amp;hello=mars&amp;foo=bar&amp;goodbye=world&amp;goodbye=mars&amp;no-value"
+
 // CAUTION: beware of arrays, the following are not quite the same
 // If you're dealing with PHP, you probably want the latter…
 uri.addSearch("foo", ["bar", "baz"]);

src/URI.js

@@ -815,7 +815,7 @@ p.hostname = function(v, build) {
     return _hostname.call(this, v, build);
 };
 
-// combination accessors
+// compound accessors
 p.host = function(v, build) {
     if (this._parts.urn) {
         return v === undefined ? '' : this;
@@ -1207,7 +1207,7 @@ p.query = function(v, build) {
 };
 p.addQuery = function(name, value, build) {
     var data = URI.parseQuery(this._parts.query);
-    URI.addQuery(data, name, value);
+    URI.addQuery(data, name, value === undefined ? null : value);
     this._parts.query = URI.buildQuery(data);
     if (typeof name !== "string") {
         build = value;

test/test.js

@@ -566,6 +566,14 @@ test("addQuery", function() {
     u.addQuery({'bam': null, 'baz': ''});
     equal(u.query(), 'foo=bar&bam&baz=', "add {name: null}");
 
+    u.query('?foo=bar');
+    u.addQuery('empty');
+    equal(u.query(), 'foo=bar&empty', "add undefined");
+
+    u.query('?foo=bar');
+    u.addQuery('empty', "");
+    equal(u.query(), 'foo=bar&empty=', "add empty string");
+
     u.query('');
     u.addQuery('some value', "must be encoded because of = and ? and #");
     equal(u.query(), 'some+value=must+be+encoded+because+of+%3D+and+%3F+and+%23', "encoding");