go 1.1 required

Now that we're using anonymous struct fields for Rate, go 1.1 really is
required.

README.md

@@ -5,9 +5,7 @@ go-github is Go library for accessing the [GitHub API][].
 **Documentation:** <http://godoc.org/github.com/google/go-github/github>  
 **Build Status:** [![Build Status](https://travis-ci.org/google/go-github.png?branch=master)](https://travis-ci.org/google/go-github)
 
-go-github is tested using Go version 1.1.  There are have been
-[reports][issue-9] of JSON marshalling errors using Go 1.0.3, at least on
-Windows 7.
+go-github requires Go version 1.1.
 
 [issue-9]: https://github.com/google/go-github/issues/9