update version number and changelog (#166)

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.6.7 (2018/10/16)
+
+* Update memoist dependency to ~> 0.16.
+
 ## 0.6.6 (2018/08/22)
 
 * Remove ruby version warnings.

lib/googleauth/version.rb

@@ -31,6 +31,6 @@ module Google
   # Module Auth provides classes that provide Google-specific authorization
   # used to access Google APIs.
   module Auth
-    VERSION = '0.6.6'.freeze
+    VERSION = '0.6.7'.freeze
   end
 end