Use a temporary directory in tests

Otherwise when you run `tox` this test will create a `data.fs` using
Python 2 and then the same test will fail on Python 3 because there
already is a `data.fs` in the current working directory, but it has an
incompatible format.

Stop calling the deprecated checkSecure method.

Fixes #134.

* Additionally test PyPy3 on TravisCI.
* Handle additional `context` argument of Python 3.7 gracefully.

Fixes #116.

Fix tests under ZODB 5.5

Based on discussion beginning https://github.com/zopefoundation/ZODB/pull/222#issuecomment-441398381

Use pickle protocol 3 on the wire.

Rename all 'async' to 'async_' for compatibility with Python 3.7.

Travis is using 3.4.6. I can't reproduce the failures locally with 3.4.4 or 3.6.4.

Fixes #113

Fixes #104.

I don't think any of those attributes were part of ZEO's public API.

Disallow using strings as addresses on Windows. Fixes #106.

No specific test case, though.

Move non-test parts of ZEO.tests.forker to ZEO._forker for ZEO.server.

FIxes #105.

Add zodbpickle to server_find_global.

Some of the tests are being killed because we don't produce any output
when running parallel tests in a layer with -v1.

The amount of warnings made it hard to see real failures.

Also use more recent PyPy, and test on Py 3.6 (which produces the
'async' warnings we'll use to fix #104)

Return early after decode error.

Closes #107.

Add coverage for ZEO module convenience functions.

Closes #102.

Closes #102.