Update Travis CI URLs

Author: atouchet

readme.md

@@ -161,8 +161,8 @@ Unless you explicitly state otherwise, any contribution intentionally submitted
 for inclusion in `packed_simd` by you, as defined in the Apache-2.0 license, shall be
 dual licensed as above, without any additional terms or conditions.
 
-[travis]: https://travis-ci.org/rust-lang-nursery/packed_simd
-[Travis-CI Status]: https://travis-ci.org/rust-lang-nursery/packed_simd.svg?branch=master
+[travis]: https://travis-ci.com/rust-lang-nursery/packed_simd
+[Travis-CI Status]: https://travis-ci.com/rust-lang-nursery/packed_simd.svg?branch=master
 [appveyor]: https://ci.appveyor.com/project/gnzlbg/packed-simd
 [Appveyor Status]: https://ci.appveyor.com/api/projects/status/hd7v9dvr442hgdix?svg=true
 [Latest Version]: https://img.shields.io/crates/v/packed_simd.svg