Avoid creating soap:Header container when there are no children
This time including the matching fixture changes to remove <soap:Header></soap:Header>
Added support for header and security fixtures in request/response tests, and added tests for header optionality
Merge branch 'master' of github.com:shelbys/node-soap

* 'master' of github.com:shelbys/node-soap:
  Added support for header and security fixtures in request/response tests, and added tests for header optionality
  This time including the matching fixture changes to remove <soap:Header></soap:Header>
  Avoid creating soap:Header container when there are no children