py2.6 compatability; fallback to trying ordereddict.OrderedDict if collections.OrderedDict is not available
Merge remote-tracking branch 'drpoovilleorg/master' into develop
Check for Py2.6 in setup.py; then add ordereddict to install_requires.
Remove dependency_link print statements from setup.py.
Update setup.py docs requires: repoze.sphinx → sphinxcontrib-fulltoc.
Remove unicode characters preventing manpage and LaTeX Sphinx builds.
Clarify a bit of and/or logic in _parsers._check_options().
Refactor _util._is_file to handle detached sigs and data on stdin.

When gnupg.GPG.verify_file() was changed recently to take the filename
of the signature file as an argument to GnuPG, and then take the data
file to be verified on stdin, the parser in _parsers._check_options()
would call _util._is_file(), which would return False and log an error
that "'-' is not a file!". This fixes that issue by catching OSError and
treating it differently.

Additionally, I renamed the _util._is_file() parameter
`input`→`filename` to avoid overriding a builtin method.

I also replaced the `assert` lines with explicit checks, because
`assert`s are stripped out when the Python interpreter is run with -OO.

 * FIXES an issue with verification of detached signatures whose
   datafiles are read from stdin.
Fix issue with detached sig verification not writing verify output.

In the method `gnupg.GPG.verify_file()`, the `writer` was improperly
initialised: `_util._threaded_copy_data` was being given a filename when
it expects an open `file` object which it can read() from. Additionally,
the `writer` parameter was missing from the call to
`gnupg.GPG._collect_output()`, so even if it had been properly
initialised, the output would not have been written to the stdin of the
thread GnuPG was being called within.
Rewrite verification unittests to use correct parameters