added param names to completion items (see also #7)

test/completion/named_param.py

@@ -0,0 +1,10 @@
+""" named params:
+>>> def a(abc): pass
+>>> a(abc=3)  # <- this stuff
+"""
+
+def a(abc):
+    pass
+
+#? 5 ['abc']
+a(abc)