[CHANGELOG] Fix an error in version numbers (thx @zygoat)

CHANGELOG.md

@@ -1,8 +1,20 @@
 _You can download previous versions [here](https://github.com/AliSoftware/OHHTTPStubs/tags) and latest version [here](https://github.com/AliSoftware/OHHTTPStubs/zipball/master) (ZIP files generated by GitHub on the fly)_
 
+## Master
+
+* Use `application/json` instead of `text/json` in `README`'s example ([#75](https://github.com/AliSoftware/OHHTTPStubs/pull/75))
+
+## [3.1.7](https://github.com/AliSoftware/OHHTTPStubs/releases/tag/3.1.7)
+
+* Added `DEFINES_MODULE` Flag to be easily imported in Swift ([#74](https://github.com/AliSoftware/OHHTTPStubs/pull/74))
+
+_(I also moved [Travis-CI build system](https://travis-ci.org/AliSoftware/OHHTTPStubs) so it now uses `xcpretty` instead of `xctool` to run Unit Tests)_
+
 ## [3.1.6](https://github.com/AliSoftware/OHHTTPStubs/releases/tag/3.1.6)
 
-* Added `DEFINES_MODULE` Flag to be easily imported in Swift [#74](https://github.com/AliSoftware/OHHTTPStubs/pull/74)
+* Fixed issue with the main thread stalling when an `NSException` was raised in the response block
+* Fixed an issue with `OHHTTPStubs/XCTestExpectation` conditional compilation in Xcode 6.0 & OSX SDK.  
+  _(the condition was previously testing available SDKs instead of Xcode version, which led to errors with Xcode 6.0 not having the latest 10.10 SDK yet, but still having the `XCTextExpectation` already anyway)_
 
 ## [3.1.5](https://github.com/AliSoftware/OHHTTPStubs/releases/tag/3.1.5)