Added PortNumber implicit in Server, HtmlUnit, Firefox, Safari, Chrome, and InternetExplorer NoArgs in MixedFixtures, and make MixedSpec to mixin WsScalaTestClient also.
Merge branch 'MixedFixtures-PortNumber' of https://github.com/cheeseng/scalatestplus-play

Conflicts:
	src/main/scala/org/scalatestplus/play/MixedFixtures.scala