Bump version to 0.3.1
Bump version to 0.3.1

codehs/pep257,Nurdok/pep257,jbeezley/pep257,GreenSteam/pep257,bagelbits/pep257,bartvm/pep257,glennmatthews/pep257,PyCQA/pydocstyle,tescalada/pydocstyle,jayvdb/pep257,jmullan/pep257,13steinj/pep257,pombredanne/pep257,Nurdok/pydocstyle,farmersez/pydocstyle