Add Appveyor CI badge to the README (#723)

README.md

 # Poetry: Dependency Management for Python
 # Poetry: Dependency Management for Python
 
 
-![Poetry build status](https://travis-ci.org/sdispater/poetry.svg)
-
 Poetry helps you declare, manage and install dependencies of Python projects,
 Poetry helps you declare, manage and install dependencies of Python projects,
 ensuring you have the right stack everywhere.
 ensuring you have the right stack everywhere.
 
 
@@ -9,6 +7,9 @@ ensuring you have the right stack everywhere.
 
 
 It supports Python 2.7 and 3.4+.
 It supports Python 2.7 and 3.4+.
 
 
+[![Unix Build Status](https://img.shields.io/travis/sdispater/poetry.svg?label=Unix)](https://travis-ci.org/sdispater/poetry)
+[![Windows Build Status](https://img.shields.io/appveyor/ci/sdispater/poetry.svg?label=Windows)](https://ci.appveyor.com/project/sdispater/poetry)
+
 ## Installation
 ## Installation
 
 
 Poetry provides a custom installer that will install `poetry` isolated
 Poetry provides a custom installer that will install `poetry` isolated