fix to BuildQueryString; params.go unit tests
diff --git a/params.go b/params.go
index f10c2db..c01c9e5 100644
--- a/params.go
+++ b/params.go
@@ -94,7 +94,7 @@
 
 		}
 		// URL encode the string for safety.
-		s := url.QueryEscape(strings.Join(optsSlice, "&"))
+		s := strings.Join(optsSlice, "&")
 		if s != "" {
 			s = "?" + s
 		}