Add coverage for ZEO module convenience functions.

Closes #102.

Closes #102.

fix ZopeUndo.Prefix decode on python 2

Use python_requires and extras_require for version-specific deps

Fixes #93.
Fixes #92

Example:

```
$ pip install .
Processing /.../ZEO
ZEO requires Python '>=2.7.9,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*' but the running Python is 3.3.6`
```

runzeo clears socket files no matter what type of string address is

We need to use six.string_types in a few other places to account for the change in ZConfig. unix_domain_sockets() was failing before this on Python 2.

They now expire in the year 4755.

Fixes #90

Also remove an unused and duplicate import from that file and the
redundant `test_suite` declaration from the test file. There was also
a duplicate method definition in the test file that was removed.

Make all classes new-style. This is especially good for PyPy

See https://github.com/zopefoundation/ZODB/pull/160 for rationale.

Also restore PyPy to the build matrix.

- Better intro

- ReST improvements

- Spelling

- Less misleading WRT daemonization

- Removed dead log-configuration link

Fix (maybe) zeoctl and remove zeopasswd

Although it's hard to tell because IDK how to make earlier versions work.

Msgpack

AttributeError 'server' when StorageServer creation fails

Thanks!