Another approach to pull request #121; allow for SOAPAction HTTP headers to be ignored for routing

Based on the discussion from pull request #121, I came up with a different approach for how to work around the case where the SOAPAction HTTP header differs from the SOAP Body action.

This introduces a configuration option, `soap_action_routing`.  This option is true by default, and is used by `lib/wash_out/router.rb` to decide whether to use the SOAPAction header (if present) to route the incoming requests to the appropriate controller action.  If **true**, then wash_out will behave just as it does without this pull request.  If **false**, then wash_out will instead perform the routing based only on what is in the SOAP Body.  This latter behavior conforms to the SOAP 1.1 specification regarding the proper handling of a SOAPAction header by a SOAP service.

Obviously you'll want to ignore the gem version change I made.