Added Travis build status image to readme
Added Travis build status image to readme

jhericks/jjwt,hendrosteven/jjwt,josebarrueta/jjwt,robertjd/jjwt,tachang/jjwt,jwtk/jjwt,brentstormpath/jjwt,reinaldohorie/jjwt,ChiralBehaviors/jjwt,dogeared/jjwt