Adding bearer security type
Exporting security type for usage
Added checking if there is input and output for operations under bindings section

There are situations where binding operation does not have input and/or output. In this situation module throws following exception:
Caught exception: TypeError: Cannot read property '$name' of null
Example of such operation defined in XML under "wsdl:binding" might be:
<wsdl:operation name="WsServerException">
  <soap:operation soapAction=""/>
  <wsdl:fault name="WsServerExceptionFault">
    <soap:fault name="WsServerExceptionFault" use="literal"/>
  </wsdl:fault>
</wsdl:operation>
Merge pull request #454 from diegossilveira/duplicated-xsd-namespace

Fixing XSD conflict on imports with same namespace
Merge pull request #455 from PhilipHansen/master

Add Support for HTTP Authentication type Bearer
Merge pull request #457 from BonneVoyager/master

Added checking if there is input and output for operations under bindings section.
Merge branch 'master' of github.com:vpulim/node-soap