Eliminate the trailing newlines and blank spaces (the code called them
"a stupid artifact").

Include the name of the defining interface (so the user can easily look up
any requirements on the attribute) and, for methods, the expected
signature (no more guessing about how many arguments are required!).

This is implemented by giving Attribute and Method useful reprs and strs.
Previously, they just had the defaults.

Fixes #170

Fix verification for methods of builtin types with pseudo-default args on PyPy

On PyPy2, they are ignored (like on CPython), but on PyPy3 they can
actually be validated.

Fixes #118

Add __all__ to all modules.

Fixes #153

The items that went in each ``__all__`` are based on what is
documented:

 $ rg --no-filename 'import' docs/ -trst | tr -s "[:blank:]" | sort | uniq | grep zope
 >>> from pprint import pprint
 >>> from zope.interface import *
 >>> from zope.interface import Interface
 >>> from zope.interface import Interface, Attribute, implementer
 >>> from zope.interface import alsoProvides
 >>> from zope.interface import classImplements
 >>> from zope.interface import classImplementsOnly
 >>> from zope.interface import directlyProvidedBy
 >>> from zope.interface import directlyProvides
 >>> from zope.interface import implementedBy
 >>> from zope.interface import implementer
 >>> from zope.interface import implementer_only
 >>> from zope.interface import noLongerProvides
 >>> from zope.interface import providedBy
 >>> from zope.interface import provider
 >>> from zope.interface.adapter import AdapterRegistry
 >>> from zope.interface.declarations import Declaration
 >>> from zope.interface.declarations import InstanceDeclarations
 >>> from zope.interface.declarations import ProvidesClass
 >>> from zope.interface.declarations import named
 >>> from zope.interface.exceptions import BrokenImplementation
 >>> from zope.interface.exceptions import Invalid
 >>> from zope.interface.interface import Specification
 >>> from zope.interface.interface import adapter_hooks
 >>> from zope.interface.verify import verifyObject
 >>> import gc
 >>> import zope.interface

And also some personal judgement about what the public API is that I'm
more than happy to have reviewed.

Performance optimization in _lookup _lookupAll and _subscriptions