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Handle file-like objects with integer name attribute

When io.BufferedReader (and others) are init-ed based on a file
descriptor, their name attribute will be an integer. Handle these
objects by explicitly checking for an integer type in guess_format() and
setting sane values (empty strings).

We don't trap an exception because Python 2 and 3 throw different types;
AttributeError and TypeError, respectively. So, this way seemed cleaner.

A trailing comma resulted in Entry.pathname being a tuple instead
of a string when using Entry.from_archive() in Python 2.

This partially reverts 5013165958 ("Fix tests for python 2 and 3"),
which accounted for Entry.pathname as a tuple, instead of addressing why
it had become one.

This also adds whitespace around the assignment operator for Python 2
and 3 to look less like a keyword argument assignment (which appears to
be where the comma originally came from).

Add a high-level API test that initially focuses on various ways that
an Archive object can be directed to use a particular file:

1. filename
2. file-like object opened by name
3. file-like object opened by fileno()

The 3rd way is currently broken for Python 2 and Python 3.

Instead of using an external utility (/usr/bin/zip) and a subprocess
call, use Python's own zipfile module to create temporary zip file.

Currently, unit testing does not cleanup the temporary directory
structure that it creates. Make it more easily identifiable for manual
cleanup by adding a recognizable suffix.

Check if data is already bytes

Python 3