The Kafka dependency pulls in other dependencies that conflict. The build fails on my machine due to attempt to pull in transitive log4j dependencies that cannot be retrieved and that we don't need.

    [ERROR] Failed to execute goal on project malhar-contrib: Could not resolve dependencies for project com.datatorrent:malhar-contrib:jar:0.9.2-SNAPSHOT: The following artifacts could not be resolved: com.sun.jdmk:jmxtools:jar:1.2.1, com.sun.jmx:jmxri:jar:1.2.1: Could not transfer artifact com.sun.jdmk:jmxtools:jar:1.2.1 from/to java.net (https://maven-repository.dev.java.net/nonav/repository): No connector available to access repository java.net (https://maven-repository.dev.java.net/nonav/repository) of type legacy using the available factories WagonRepositoryConnectorFactory -> [Help 1]

Here is the modified dependency with excludes:

```
    <dependency>
      <groupId>org.apache.kafka</groupId>
      <artifactId>kafka_2.10</artifactId>
      <version>0.8.0</version>
      <exclusions>
        <exclusion>
          <groupId>org.slf4j</groupId>
          <artifactId>slf4j-log4j12</artifactId>
        </exclusion>
        <exclusion>
          <groupId>org.slf4j</groupId>
          <artifactId>slf4j-simple</artifactId>
        </exclusion>
        <exclusion>
          <groupId>log4j</groupId>
          <artifactId>log4j</artifactId>
        </exclusion>
        <exclusion>
          <groupId>org.apache.zookeeper</groupId>
          <artifactId>zookeeper</artifactId>
        </exclusion>
      </exclusions>
    </dependency>
```