print cli parse error message to let user know what is missing (#258)

I merged this and will fix build (forbidden apis due to System.out usage) in a followup commit.

Author: maxandersen

src/main/java/de/thetaphi/forbiddenapis/cli/CliMain.java

@@ -154,6 +154,7 @@ public CliMain(String... args) throws ExitException {
         throw new ExitException(EXIT_SUCCESS);
       }
     } catch (org.apache.commons.cli.ParseException pe) {
+      System.out.println(pe.getMessage());
       printHelp(options);
       throw new ExitException(EXIT_ERR_CMDLINE);
     }