v3.0.0
bumps marshmallow version and argschema dependency (#112) * bumps marshmallow version and argschema dependency * renames container to inner (new in marshmallow 3.0.0rc8) * extends marshmallow range down to 3.0.0
bumps marshmallow version and argschema dependency (#112) * bumps marshmallow version and argschema dependency * renames container to inner (new in marshmallow 3.0.0rc8) * extends marshmallow range down to 3.0.0