Add link on travis CI badge

Author: AArnott

README.md

@@ -4,7 +4,7 @@ Specialized .NET Stream classes
 [![NuGet package](https://img.shields.io/nuget/v/Nerdbank.Streams.svg)](https://nuget.org/packages/Nerdbank.Streams)
 
 [![Build status](https://ci.appveyor.com/api/projects/status/849r1unf4tnjbpy8?svg=true)](https://ci.appveyor.com/project/AArnott/nerdbank-fullduplexstream)
-![Travis (.org)](https://api.travis-ci.org/AArnott/Nerdbank.Streams.svg?branch=master)
+[![Travis (.org)](https://api.travis-ci.org/AArnott/Nerdbank.Streams.svg?branch=master)](https://travis-ci.org/AArnott/Nerdbank.Streams)
 [![codecov](https://codecov.io/gh/AArnott/Nerdbank.Streams/branch/master/graph/badge.svg)](https://codecov.io/gh/AArnott/Nerdbank.Streams)
 
 ## Features