Update README.md

Author: sfackler

README.md

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 # rust-native-tls
 
-[![CircleCI](https://circleci.com/gh/sfackler/rust-native-tls.svg?style=shield)](https://circleci.com/gh/sfackler/rust-native-tls) [![Build Status](https://travis-ci.org/sfackler/rust-native-tls.svg?branch=master)](https://travis-ci.org/sfackler/rust-native-tls)
+[![CircleCI](https://circleci.com/gh/sfackler/rust-native-tls.svg?style=shield)](https://circleci.com/gh/sfackler/rust-native-tls)
 
 [Documentation](https://docs.rs/native-tls)