Changed README to reflect that ServerAssertion is an abstract class + added serialVersionUID
Changed README to reflect that ServerAssertion is an abstract class +
added serialVersionUID

CSchulz/arquillian-extension-warp,arquillian/arquillian-extension-warp,petrandreev/arquillian-extension-warp,CSchulz/arquillian-extension-warp,arquillian/arquillian-extension-warp