1.9.0

• #820
• #822
• #825
• Update versions of dependencies

See the details in 1.9.0 milestone.

The binaries can be found on Maven Central:

<dependency>
    <groupId>com.sap.oss.phosphor</groupId>
    <artifactId>fosstars-rating-core</artifactId>
    <version>1.9.0</version>
</dependency>