Because it is a snapshot release, it is not in the central repository but in the sonatype snapshots one:
If you want your maven project to download it from this location you have to add the repository to your pom file:
<repositories>
<repository>
<id>sonatype</id>
<url>http://oss.sonatype.org/content/repositories/snapshots</url>
<snapshots><enabled>true</enabled></snapshots>
<releases><enabled>false</enabled></releases>
</repository>
</repositories>