Update CHANGELOG for 0.7.0

Author: henryiii

CHANGELOG.md

@@ -1,4 +1,10 @@
-## Version 0.7.0 (in progress)
+## Version 0.7.0
+
+This version removes deprecated functionality, and has several backend
+improvements. The most noticeable user-facing change is the multithreaded fill
+feature, which can enable significant speedups when you have a dataset that is
+much larger than the number of bins in your histogram and have free cores to
+use. Several small bugs have been fixed.
 
 #### User changes
 

README.md

@@ -12,7 +12,9 @@
 [![Conda-Forge](https://img.shields.io/conda/vn/conda-forge/boost-histogram)][conda-link]
 [![Scikit-HEP][sk-badge]](https://scikit-hep.org/)
 
-Python bindings for [Boost::Histogram][] ([source][Boost::Histogram source]), a C++14 library. This should become one of the [fastest libraries][] for histogramming, while still providing the power of a full histogram object.
+Python bindings for [Boost::Histogram][] ([source][Boost::Histogram source]), a
+C++14 library. This should become one of the [fastest libraries][] for
+histogramming, while still providing the power of a full histogram object.
 
 ## Installation