[readme] Update Travis CI badge and link url

travis-ci.org is deprecated and replaced by app.travis-ci.com for a while

README.md

 <a href="https://github.com/nvm-sh/logos"><img alt="nvm project logo" src="https://raw.githubusercontent.com/nvm-sh/logos/HEAD/nvm-logo-color.svg" height="50" /></a>
 
-# Node Version Manager [![Build Status](https://travis-ci.org/nvm-sh/nvm.svg?branch=master)][3] [![nvm version](https://img.shields.io/badge/version-v0.39.3-yellow.svg)][4] [![CII Best Practices](https://bestpractices.coreinfrastructure.org/projects/684/badge)](https://bestpractices.coreinfrastructure.org/projects/684)
+# Node Version Manager [![Build Status](https://app.travis-ci.com/nvm-sh/nvm.svg?branch=master)][3] [![nvm version](https://img.shields.io/badge/version-v0.39.3-yellow.svg)][4] [![CII Best Practices](https://bestpractices.coreinfrastructure.org/projects/684/badge)](https://bestpractices.coreinfrastructure.org/projects/684)
 
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@@ -900,7 +900,7 @@ To change the user directory and/or account name follow the instructions [here](
 
 [1]: https://github.com/nvm-sh/nvm.git
 [2]: https://github.com/nvm-sh/nvm/blob/v0.39.3/install.sh
-[3]: https://travis-ci.org/nvm-sh/nvm
+[3]: https://app.travis-ci.com/nvm-sh/nvm
 [4]: https://github.com/nvm-sh/nvm/releases/tag/v0.39.3
 [Urchin]: https://git.sdf.org/tlevine/urchin
 [Fish]: https://fishshell.com