Fix/improve the SSL configuration

- Do not extend config.express.serverOptions with config.ssl before
  the config validation is done: the former is undefined by default
  (#843) and that's OK as it would fire a validation warning otherwise.

- Use _.merge instead of the undefined _.recursive.defaults to set the
  default values of config.express.serverOptions (#844). Use _.extend
  if the serverOptions wasn't defined by the user's config.
added suport for winston adapters
Added CONTRIBUTE.md to help improve contributions
>>
>> The CONTRIBUTE.md message will now always show up whenever opening a PR or
>> issue.
>>
>> Closes #717
Merge pull request #869 from yoshuawuyts/master

Added CONTRIBUTE.md to help improve contributions
Merge pull request #845 from wolneykien/master

Fix/improve the SSL configuration
Merge pull request #851 from sazze/master

added suport for winston adapters