Don't explode on wildcard types

[swankjesse]

Given this input:

    @Provides Class<? extends MyInterface> provideClassImpl() {
        return InterfaceImpl.class;
    }

Dagger fails like this:

java.lang.UnsupportedOperationException: Uninjectable type ? extends com.sample.app.di.MyInterface
E/AndroidRuntime( 6701):        at dagger.internal.Keys.typeToString(Keys.java:169)
E/AndroidRuntime( 6701):        at dagger.internal.Keys.typeToString(Keys.java:161)
E/AndroidRuntime( 6701):        at dagger.internal.Keys.get(Keys.java:79)
E/AndroidRuntime( 6701):        at dagger.internal.Keys.get(Keys.java:111)

We should handle wildcard types!