DOC added standard plotting style to whatsnew

Author: eigenfoo

WHATSNEW.md

@@ -31,6 +31,8 @@ This is a major release from `0.7.0`, and all users are recoommended to upgrade.
    Jupyter notebooks. By [George Ho](https://github.com/eigenfoo).
  - Data loader migration: all data loaders have been migrated from `pyfolio` to
    `empyrical`. By [James Christopher](https://github.com/jameschristopher).
+ - Improved plotting style: fixed issues with formatting and presentation of
+   plots. By [George Ho](https://github.com/eigenfoo).
 
 ## v0.7.0 (Jan 28th, 2017)