Set release date

doc/Changelog.md

@@ -2,7 +2,7 @@
 
 ## 2.2.0
 
-**Not yet released**
+Released 2017-09-24
 
 * Added possibility for actions' `apply()` or `apply0()`-methods to return a `bool` which is then used to determine overall success or failure of the rule to which such an action was attached.
 * Added [`<tao/pegtl/contrib/parse_tree.hpp>`](Contrib-and-Examples.md#taopegtlcontribparse_treehpp) and the [`examples/parse_tree.cpp`](Contrib-and-Examples.md#srcexamplepegtlparse_treecpp) application that shows how to build a [parse tree](https://en.wikipedia.org/wiki/Parse_tree). The example goes beyond a traditional parse tree and demonstrates how to select which nodes to include in the parse tree and how to transform the nodes into an [AST](https://en.wikipedia.org/wiki/Abstract_syntax_tree)-like structure.