(MAINT) Fix typo, it's ruby-load-path, not paths

Setting ruby-load-paths instead of ruby-load-path results in:
Caused by: java.lang.Exception: JRuby service missing config value 'ruby-load-path'
Merge pull request #307 from jasperla/load-path

(MAINT) Fix typo, it's ruby-load-path, not paths