feat(util.to_query_str): Smart handling of lists

This patch improves to_query_str so it can recognize instances of
list and convert it to a comma-delimited string value.

Closes #152

falcon/tests/test_utils.py

@@ -34,6 +34,18 @@ class TestFalconUtils(testtools.TestCase):
             falcon.to_query_str({'limit': 10}),
             '?limit=10')
 
+        self.assertEquals(
+            falcon.to_query_str({'things': [1, 2, 3]}),
+            '?things=1,2,3')
+
+        self.assertEquals(
+            falcon.to_query_str({'things': ['a']}),
+            '?things=a')
+
+        self.assertEquals(
+            falcon.to_query_str({'things': ['a', 'b']}),
+            '?things=a,b')
+
     def test_pack_query_params_several(self):
         garbage_in = {
             'limit': 17,

falcon/util.py

@@ -63,7 +63,8 @@ def to_query_str(params):
     Args:
         params: dict of simple key-value types, where key is a string and
             value is a string or something that can be converted into a
-            string.
+            string. If value is a list, it will be converted to a comma-
+            delimited string (e.g., thing=1,2,3)
 
     Returns:
         A URI query string starting with '?', or and empty string if there
@@ -81,6 +82,8 @@ def to_query_str(params):
             v = 'true'
         elif v is False:
             v = 'false'
+        elif isinstance(v, list):
+            v = ','.join([str(i) for i in v])
         else:
             v = str(v)