Update changelog.

Changelog

diff --git a/Changelog b/Changelog
index 526756b..98247e7 100644
--- a/Changelog
+++ b/Changelog
@@ -1,3 +1,6 @@
+2015-05-19:
+  Rename 'src' directory to 'double-conversion'.
+
 2014-03-08:
   Update version number for cmake.
   Support shared libraries with cmake.