added javascript example using the interface
removed a few unused variables, changed on ifs, {}, etc based on PMD findings
changed loggers to private static (that was left over from vert.x 2 it seems)
fixed MailConfig.equals to use string.equals (findbugs finding)
fixed NPE in Json to MailConfig constructor

Signed-off-by: alexlehm <alexlehm@gmail.com>
Ignore two tests since they do not work without credentials

Signed-off-by: alexlehm <alexlehm@gmail.com>