Add knob BLANK_LINES_AROUND_TOP_LEVEL_DEFINITION

to modify the number of blank lines around top level function and class definitions.
Closes #527
diff --git a/CHANGELOG b/CHANGELOG
index 486c64f..d278a6d 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -9,6 +9,8 @@
   get their own line.
 - Added `CONTINUATION_ALIGN_STYLE` knob to choose continuation alignment style
   when `USE_TABS` is enabled.
+- Add 'BLANK_LINES_AROUND_TOP_LEVEL_DEFINITION' knob to control the number
+  of blank lines between top-level function and class definitions.
 ### Fixed
 - Don't split ellipses.