[Appveyor] Add README badge for master branch.

Author: metaskills

README.md

@@ -1,8 +1,7 @@
 
 # ActiveRecord SQL Server Adapter. For SQL Server 2012 And Higher.
 
-[![Gem Version](http://img.shields.io/gem/v/activerecord-sqlserver-adapter.svg?style=flat)](https://rubygems.org/gems/activerecord-sqlserver-adapter)
-[![Gitter chat](https://img.shields.io/badge/%E2%8A%AA%20GITTER%20-JOIN%20CHAT%20%E2%86%92-brightgreen.svg?style=flat)](https://gitter.im/rails-sqlserver/activerecord-sqlserver-adapter)
+[![Build status](https://ci.appveyor.com/api/projects/status/mtgbx8f57vr7k2qa/branch/master?svg=true)](https://ci.appveyor.com/project/rails-sqlserver/activerecord-sqlserver-adapter/branch/master) [![Gem Version](http://img.shields.io/gem/v/activerecord-sqlserver-adapter.svg?style=flat)](https://rubygems.org/gems/activerecord-sqlserver-adapter) [![Gitter chat](https://img.shields.io/badge/%E2%8A%AA%20GITTER%20-JOIN%20CHAT%20%E2%86%92-brightgreen.svg?style=flat)](https://gitter.im/rails-sqlserver/activerecord-sqlserver-adapter)
 
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