Add 'ALLOW_MULTILINE_LAMBDAS' style option

Allows a lambda to be formatted onto multiple lines.

Closes #225
diff --git a/CHANGELOG b/CHANGELOG
index ce38b22..ab62a36 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -4,7 +4,9 @@
 
 ## [0.7.0] UNRELEASED
 ### Added
-- Support for 3.5.
+- Support for Python 3.5.
+- Add 'ALLOW_MULTILINE_LAMBDAS' which allows lambdas to be formatted onto
+  multiple lines.
 
 ### Fixed
 - Lessen penalty for splitting before a dictionary keyword.