checking for null or empty param before set
adding a simple test case
changing lucas' suggestions
adding vraptor-java8 plugin on EN page
adding vraptor-java8 plugin on PT page
adding Otavio's description
Merge pull request #631 from caelum/nullHeaderParams

fixing problem with null headers
Merge pull request #669 from caelum/addingVRaptorJava8Plugin

Adding vraptor-java8 plugin on docs