fix(README): phrase the note abouth webpack v2 in a slightly better way (#145)

Author: halfzebra

README.md

@@ -17,7 +17,7 @@ Writing webpack configs is brittle and error-prone. This package provides a [joi
 
 You're very welcome to give [feedback](https://github.com/js-dxtools/webpack-validator/issues) & [PR's](https://github.com/js-dxtools/webpack-validator).
 
-**Note that as of webpack v2 (currently in beta), configuration validation is baked in.**
+**Note: webpack v2 has built-in validation for configuration.**
 
 ### Example
 Take this simple webpack config. It has a tiny, hard to spot error. Can you find it?