passing protocol to build() should be ignored

[cmawhorter]

currently, calling urn = create('something'); urn.build({ protocol: 'else' }) works but nothing can be done with the result. format ignores the changed protocol.

build should be updated to also ignore protocol to bring it inline with everything else.

[cmawhorter]

opted to add an options object that allows a more explicit and strict handling of protocol mismatch:

formatUrn(
  'blah',
  components,
  separator,
  { protocol: 'invalid', nid: 'i', nss: 's' },
  {strictProtocol: true} // will lead to an error being thrown because parsed doesn't match expected (blah)
);

by default, the backwards compatible behavior is maintained i.e. it just accepts the different value