Add configuration option for wstrust version

I've modified strategy.js and wsFederation.js to allow for an additional configuration option when initializing the strategy to specify the wstrust version being used for the implementation.

I'm using wst1.3 and discovered that the namespace used to extract the token is specific to wst1.2.  You can see the details here:

http://docs.oasis-open.org/imi/identity/v1.0/identity.html#_Ref212806433

The intent of my change to is leave the behavior exactly as is currently, unless the new option is specified.  If an option other than 'wst1.3' is specified, it will also revert to the existing behavior.

Please let me know if you have any questions/comments, and if you do accept the changes, it would much appreciated if you pushed them to npm.

Thanks!
Andrew