Readme improvements (#557)

* [README] Use tools.ietf.org for displaying RFC7932

tools.ietf.org has HTML links which is helpful when reading
in browser

* [README] Add appveyor badge
diff --git a/README.md b/README.md
index 637d52b..a59bb58 100644
--- a/README.md
+++ b/README.md
@@ -8,14 +8,15 @@
 currently available general-purpose compression methods. It is similar in speed
 with deflate but offers more dense compression.
 
-The specification of the Brotli Compressed Data Format is defined in [RFC 7932](https://www.ietf.org/rfc/rfc7932.txt).
+The specification of the Brotli Compressed Data Format is defined in [RFC 7932](https://tools.ietf.org/html/rfc7932).
 
 Brotli is open-sourced under the MIT License, see the LICENSE file.
 
 Brotli mailing list:
 https://groups.google.com/forum/#!forum/brotli
 
-[![Build Status](https://travis-ci.org/google/brotli.svg?branch=master)](https://travis-ci.org/google/brotli)
+[![TravisCI Build Status](https://travis-ci.org/google/brotli.svg?branch=master)](https://travis-ci.org/google/brotli)
+[![AppVeyor Build Status](https://ci.appveyor.com/api/projects/status/github/google/brotli?branch=master&svg=true)](https://ci.appveyor.com/project/szabadka/brotli)
 
 ### Build instructions