Add the version table

The table shows the compatible RxJava version for RxScala.
Are you sure? In the POM at http://search.maven.org/#artifactdetails|io.reactivex|rxscala_2.11|0.23.0|jar, I read

        <dependency>
            <groupId>io.reactivex</groupId>
            <artifactId>rxjava</artifactId>
            <version>1.0.2</version>
        </dependency>

so I guess it will only work with `1.0.2`...