You are a bit mixing dependencies. Try to follow this tutorial in order to set up Graphene.
You should end up with following maven dependencies:
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.jboss.arquillian</groupId>
<artifactId>arquillian-bom</artifactId>
<version>1.1.2.Final</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<dependency>
<groupId>org.jboss.arquillian.extension</groupId>
<artifactId>arquillian-drone-bom</artifactId>
<version>1.2.3.Final</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<dependency>
<groupId>org.jboss.arquillian.selenium</groupId>
<artifactId>selenium-bom</artifactId>
<version>2.39.0</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<dependency>
<groupId>org.jboss.arquillian.graphene</groupId>
<artifactId>graphene-webdriver</artifactId>
<version>2.0.1.Final</version>
<type>pom</type>
<scope>test</scope>
</dependency>
</dependencies>