docs: fix TravisCI badge in README

The badge pointed to the old location of the repo under posborne's
account, this changes the link to point to the current location.

Author: ekmecic

README.md

@@ -1,7 +1,7 @@
 rust-sysfs-pwm
 ==============
 
-[![Build Status](https://travis-ci.org/posborne/rust-sysfs-pwm.svg?branch=master)](https://travis-ci.org/posborne/rust-sysfs-pwm)
+[![Build Status](https://travis-ci.org/rust-embedded/rust-sysfs-pwm.svg?branch=master)](https://travis-ci.org/posborne/rust-sysfs-pwm)
 [![Version](https://img.shields.io/crates/v/sysfs-pwm.svg)](https://crates.io/crates/sysfs-pwm)
 [![License](https://img.shields.io/crates/l/sysfs-pwm.svg)](https://github.com/posborne/rust-sysfs-pwm/blob/master/README.md#license)