py-attrs: updated to 18.1.0

18.1.0:
- x=X(); x.cycle = x; repr(x) will no longer raise a RecursionError, and will instead show as X(x=...).
- attr.ib(factory=f) is now syntactic sugar for the common case of attr.ib(default=attr.Factory(f)).
- Added attr.field_dict() to return an ordered dictionary of attrs attributes for a class, whose keys are the attribute names.
- The order of attributes that are passed into attr.make_class() or the these argument of @attr.s() is now retained if the dictionary is ordered (i.e. dict on Python 3.6 and later, collections.OrderedDict otherwise).
  Before, the order was always determined by the order in which the attributes have been defined which may not be desirable when creating classes programatically.
- In slotted classes, __getstate__ and __setstate__ now ignore the __weakref__ attribute.
- Setting the cell type is now completely best effort.
  This fixes attrs on Jython.
  We cannot make any guarantees regarding Jython though, because our test suite cannot run due to dependency incompatabilities.
- If attr.s is passed a *these* argument, it will not attempt to remove attributes with the same name from the class body anymore.
- The hash of attr.NOTHING is now vegan and faster on 32bit Python builds.
- The overhead of instantiating frozen dict classes is virtually eliminated.
- Generated __init__ methods now have an __annotations__ attribute derived from the types of the fields.
- We have restructured the documentation a bit to account for attrs' growth in scope.

(adam)