derives for ToJava or FromJava assume `java` is in scope

[Niko Matsakis]

While writing out some examples I found that this

#[derive(Debug, duchess::ToJava)] // <-- derive ToJava
#[java(auth.HttpRequest)] // <-- declares the Java class we convert into
pub struct HttpRequest {
    pub verb: String,
    pub path: String,
}

fails to compile unless you have duchess::java in scope, which seems bad