Two of the tests for _p_serial weren't catching what we thought they were.

Deleted _makeOctets since we have native literals everywhere.

Two bug fixes for pure-Python mode: deleting _p_oid and deleting *any* _p attribute.

Test the docs on Python 2 and 3 using manuel. This gets a lot of coverage of tests.attrhooks, tests.cucumbers and tests.utils.

Build CFFI modules the modern way.

Switch to zope.testrunner from 'python setup.py test' and 'nose'.

Both are essentially deprecated.

This is a step in producing usable coverage numbers.

(Also remove cp33 from the manylinux build. This was missed in https://github.com/zopefoundation/persistent/pull/74)

Add support for Python 3.7 and drop 3.3

[skip ci]

[skip ci]

Update url in setup.py

Fixes #71

Also fix the lint warnings in setup.py: consistent use of continued indentation and trailing commas.

Change cPickleCache to use PER_TypeCheck

Instead of testing object sizes.

This matches what the pure Python implementation does and is a
stronger test that the object really is compatible with the cache.
Previously, an object could potentially include ``cPersistent_HEAD``
and *not* set ``tp_base`` to ``cPersistenceCAPI->pertype`` and still
be eligible for the pickle cache; that is no longer the case.

This resolves several compiler warnings:

persistent/cPickleCache.c:521:43: warning: comparison of integers of different signs: 'Py_ssize_t' (aka 'long') and 'unsigned long' [-Wsign-compare]
                (v->ob_type->tp_basicsize >= sizeof(cPersistentObject))
                 ~~~~~~~~~~~~~~~~~~~~~~~~ ^  ~~~~~~~~~~~~~~~~~~~~~~~~~
persistent/cPickleCache.c:709:39: warning: comparison of integers of different signs: 'Py_ssize_t' (aka 'long') and 'unsigned long' [-Wsign-compare]
    else if (v->ob_type->tp_basicsize < sizeof(cPersistentObject))

Fixes #69.

Update documentation links.

Added a link to readable documentation, viewable from GitHub.

Fix possibility of rare crash during dealloc. Fixes #66

remove build files in manylinux builds

CI setup for manylinux wheels on tagged commit