Update appveyor master badge.

Author: vprus

README.md

@@ -14,7 +14,7 @@ Distributed under the [Boost Software License, Version 1.0](http://www.boost.org
 
 |Branch          | Travis | Appveyor | Coverity Scan | codecov.io | Deps | Docs | Tests |
 |:-------------: | ------ | -------- | ------------- | ---------- | ---- | ---- | ----- |
-|[`master`](https://github.com/boostorg/program_options/tree/master) | [![Build Status](https://travis-ci.org/boostorg/program_options.svg?branch=master)](https://travis-ci.org/boostorg/program_options) | [![Build status](https://ci.appveyor.com/api/projects/status/upf5c528fy09fudk?svg=true)](https://ci.appveyor.com/project/jeking3/date-time-1evbf) | [![Coverity Scan Build Status](https://scan.coverity.com/projects/14908/badge.svg)](https://scan.coverity.com/projects/boostorg-program_options) | [![codecov](https://codecov.io/gh/boostorg/program_options/branch/master/graph/badge.svg)](https://codecov.io/gh/boostorg/program_options/branch/master) | [![Deps](https://img.shields.io/badge/deps-master-brightgreen.svg)](https://pdimov.github.io/boostdep-report/master/program_options.html) | [![Documentation](https://img.shields.io/badge/docs-master-brightgreen.svg)](http://www.boost.org/doc/libs/master/doc/html/program_options.html) | [![Enter the Matrix](https://img.shields.io/badge/matrix-master-brightgreen.svg)](http://www.boost.org/development/tests/master/developer/program_options.html) 
+|[`master`](https://github.com/boostorg/program_options/tree/master) | [![Build Status](https://travis-ci.org/boostorg/program_options.svg?branch=master)](https://travis-ci.org/boostorg/program_options) | [![Build status](https://ci.appveyor.com/api/projects/status/e0quisadwh1v7ok5/branch/master?svg=true)](https://ci.appveyor.com/project/vprus/program-options/branch/master) | [![Coverity Scan Build Status](https://scan.coverity.com/projects/14908/badge.svg)](https://scan.coverity.com/projects/boostorg-program_options) | [![codecov](https://codecov.io/gh/boostorg/program_options/branch/master/graph/badge.svg)](https://codecov.io/gh/boostorg/program_options/branch/master) | [![Deps](https://img.shields.io/badge/deps-master-brightgreen.svg)](https://pdimov.github.io/boostdep-report/master/program_options.html) | [![Documentation](https://img.shields.io/badge/docs-master-brightgreen.svg)](http://www.boost.org/doc/libs/master/doc/html/program_options.html) | [![Enter the Matrix](https://img.shields.io/badge/matrix-master-brightgreen.svg)](http://www.boost.org/development/tests/master/developer/program_options.html) 
 |[`develop`](https://github.com/boostorg/program_options/tree/develop) | [![Build Status](https://travis-ci.org/boostorg/program_options.svg?branch=develop)](https://travis-ci.org/boostorg/program_options) | [![Build status](https://ci.appveyor.com/api/projects/status/e0quisadwh1v7ok5/branch/develop?svg=true)](https://ci.appveyor.com/project/vprus/program-options/branch/develop) | [![Coverity Scan Build Status](https://scan.coverity.com/projects/14908/badge.svg)](https://scan.coverity.com/projects/boostorg-program_options) | [![codecov](https://codecov.io/gh/boostorg/program_options/branch/develop/graph/badge.svg)](https://codecov.io/gh/boostorg/program_options/branch/develop) | [![Deps](https://img.shields.io/badge/deps-develop-brightgreen.svg)](https://pdimov.github.io/boostdep-report/develop/program_options.html) | [![Documentation](https://img.shields.io/badge/docs-develop-brightgreen.svg)](http://www.boost.org/doc/libs/develop/doc/html/program_options.html) | [![Enter the Matrix](https://img.shields.io/badge/matrix-develop-brightgreen.svg)](http://www.boost.org/development/tests/develop/developer/program_options.html)
 
 ### Directories