Update changelog for 3.8 release.

myronmarston · myronmarston · commit 4ef6b339bdf3 · 2018-08-04T12:43:43.000-07:00
[ci skip]
diff --git a/Changelog.md b/Changelog.md
@@ -1,5 +1,5 @@
-### Development
-[Full Changelog](http://github.com/rspec/rspec-support/compare/v3.7.1...master)
+### 3.8.0 / 2018-08-04
+[Full Changelog](http://github.com/rspec/rspec-support/compare/v3.7.1...v3.8.0)
 
 Bug Fixes:
 
