travis: allow failures on PyPy
travis: allow failures on PyPy

mafrosis/flask-security,fuhrysteve/flask-security,inveniosoftware/flask-security-fork,fmerges/flask-security,LeonhardPrintz/flask-security-fork,mafrosis/flask-security,fuhrysteve/flask-security,nfvs/flask-security,inveniosoftware/flask-security-fork,themylogin/flask-security,inveniosoftware/flask-security-fork,nfvs/flask-security,mattupstate/flask-security,LeonhardPrintz/flask-security-fork,themylogin/flask-security,fmerges/flask-security,LeonhardPrintz/flask-security-fork,mattupstate/flask-security