Maven 3.1.0 compat

The plugin does not currently work with Maven 3.1.0:

http://mail-archives.apache.org/mod_mbox/maven-dev/201307.mbox/%3CA0E902BA-DF77-4F71-99D0-A76E2660D117%40apache.org%3E

Maven is likely to restore the API in the next version, but it should be possible to adjust the plugin to use a more compatible API:

http://mail-archives.apache.org/mod_mbox/maven-dev/201307.mbox/%3CA245373B-8A4E-465D-9985-92563FC61AFE@gmail.com%3E

This patch should correct it without any adverse affects, but I'm unsure if there was a case you were trying to address with this converter that I might have missed.