Blog post for 15.6.0

**what is the change?:**
A short and sweet summary of 15.6.0 changes

**why make this change?:**
To thank community contributors and call out important changes.

**test plan:**
Visual inspection.
I also looked it over in a markdown viewer - http://dillinger.io/

**issue:**
facebook#9398

docs/_posts/2017-06-13-react-v15.6.0.md

@@ -0,0 +1,24 @@
+---
+title: "React v15.6.0"
+author: flarnie
+---
+Today we are releasing React 15.6.0. As we prepare for React 16.0, we have been fixing and cleaning up many things. This release continues to pave the way.
+
+## Improving Inputs
+
+In React 15.6.0 the 'onChange' event for inputs is a little bit more reliable and handles more edge cases, including the following:
+
+* not firing when radio button is clicked but not changed ([issue 1471](https://github.com/facebook/react/issues/1471))
+* changing an input of type 'range' with the arrow keys ([issue 554](https://github.com/facebook/react/issues/554))
+* pasting text into a text area in IE11 ([issue 7211](https://github.com/facebook/react/issues/7211))
+* auto-fill in IE11 ([issue 6614](https://github.com/facebook/react/issues/6614))
+* clearing input with 'x' button or right-click 'delete' in IE11 ([issue 6822](https://github.com/facebook/react/issues/6822))
+* not firing when characters are present in the input on render in IE11 ([issue 2185](https://github.com/facebook/react/issues/2185))
+
+Thanks to [Jason Quense](https://github.com/jquense) and everyone who helped out on those issues and PRs.
+
+# Downgrading Deprecation Warnings
+
+We are also including a couple of new warnings for upcoming deprecations. These should not affect most users, and for more details see the changelog below.
+
+After the last release, we got valuable community feedback that deprecation warnings were causing noise and failing tests. **In React 15.6, we have downgraded deprecation warnings to use 'console.warn' instead of 'console.error'.** Our other warnings will still use 'console.error' because they surface urgent issues which could lead to bugs. Unlike our other warnings, deprecation warnings can be fixed over time and won't cause problems in your app if shipped. We believe that downgrading the urgency of deprecation warnings will make your next update easier. Thanks to everyone who was involved in the discussion of this change.