Update readme with organization data

Inserts some other badges that are typically present in the other
repositories.

README.md

@@ -1,4 +1,6 @@
 # image-tiff
-[![Build Status](https://travis-ci.org/PistonDevelopers/image-tiff.svg?branch=master)](https://travis-ci.org/PistonDevelopers/image-tiff)
+[![Build Status](https://travis-ci.org/image-rs/image-tiff.svg?branch=master)](https://travis-ci.org/image-rs/image-tiff)
+[![Documentation](https://docs.rs/tiff/badge.svg)](https://docs.rs/tiff)
+[![Further crate info](https://img.shields.io/crates/v/tiff.svg)](https://crates.io/crates/tiff)
 
 TIFF decoding and encoding library in pure Rust