update travis uri

README.md

-# dlib C++ library [![Travis Status](https://travis-ci.org/davisking/dlib.svg?branch=master)](https://travis-ci.org/davisking/dlib)
+# dlib C++ library [![Travis Status](https://travis-ci.com/davisking/dlib.svg?branch=master)](https://travis-ci.com/davisking/dlib)
 
 Dlib is a modern C++ toolkit containing machine learning algorithms and tools for creating complex software in C++ to solve real world problems. See [http://dlib.net](http://dlib.net) for the main project documentation and API reference.