Apache commons-io needs to be added as dependency

In using RDFDataMgr.write(out, m, RDFFormat.JSONLD_PRETTY)

to write out a Model as jsonld, an error was generated for a missing library found in apache commons-io.  Adding

<dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.6</version>
        </dependency>

to my maven project resolved the issue.