Address reviewer comments

Author: allanrenucci

docs/blog/_posts/2017-10-02-fourth-dotty-milestone-release.md

@@ -47,14 +47,13 @@ to provide syntax highlighting, multi-line editing, history, etc.
 Since our first release, it has been possible to use Scala 2 libraries in a
 Dotty project as explained in the
 [dotty-example-project](https://github.com/smarter/dotty-example-project#getting-your-project-to-compile-with-dotty).
-Previously, we supported libraries compiled Scala 2.11, but starting with this
+Previously, we supported libraries compiled by Scala 2.11, but starting with this
 release we support Scala 2.12 instead. If your Dotty project has Scala 2
 dependencies this change should be transparent for you assuming all your
 dependencies have been published for 2.12.
 
 ### Performance work
-Over the last few weeks, we have begun work on improving compilation bit by bit
-with some good results:
+Over the last few weeks, we started working on compilation speed with some good results:
 compiling [ScalaPB](https://github.com/dotty-staging/scalapb) is now 20% faster
 than with Dotty 0.3.0-RC2. You can follow along our progress on
 http://dotty-bench.epfl.ch/.