Return the default PMD rule sets instead of an empty list.

Fixes #33 and also fixes the names/location of the default PMD rule
sets ('java/basic.xml' instead of 'java-basic.xml').

Signed-off-by: Sebastian Hoß <mail@shoss.de>
Fixed rule set location & naming

Signed-off-by: Sebastian Hoß <sebastian.hoss@ysura.com>
Merge pull request #34 from sebhoss/default_pmd_rule_sets

Return the default PMD rule sets instead of an empty list.