Change options of pdb plugin

Support --pdb-errors, --pdb-failures, and --pdb (both)

This fixes #366.
Add missing format parameter in error message
switch docs sidebar tracker link to current GitHub (instead of old Google code site)
Merge pull request #671 from emillon/master

Add missing format parameter in error message
Merge pull request #676 from ddbeck/fix_sidebar_link

Switch docs sidebar tracker link to current GitHub instead of old Google code site
Change links on docs sidebar

* Remved "Older Versions" section that contained broken links
* Fixed link to pytest
* Fixed "Current Version" link to pypi to link to current version
* Removed link to old and unused announcement mailing list

This fixes #374
xunit: don't claim to take multiple args in Tee.write()
Fix #680: xunit problem with unicode on stdout

It turns out we were trying to write unicode strings into a
cStringIO.StringIO object, which doesn't work well with unicode strings.
Instead, lets use StringIO.StringIO objects for capturing stdout and
stderr.
Fix #649: UnicodeDecodeError when an exception contains encoded strings

The issue stems from the fact that when you use a coding line in the
Python file, and raise an exception that contains unicode characters,
the message in the exception is an encoded string.  We need to get it
converted into unicode, but simply calling `unicode(ev)` doesn't work,
as that often fails with a `UnicodeDecodeError` because it assumes
`ascii` encoding by default.

This fixes the issue by trying to decode the stream as UTF-8, and uses
replacement on errors.  It's not ideal, but the best we can do since
we don't know the encoding of the message string.

Thanks to Christoph Zwerschke for the test case.
Fix #687: verbosity is not a flag

The issue is that `nosetests.cfgToArg()` was treating the verbosity flag
as a boolean when you set the value to `1` in `setup.cfg`.  Instead of
using the `flag()` helper, let's consult the option object and see if
the action is `store_true` or `store_false`.
Merge pull request #666 from Infinidat/366

Make `--pdb` launch pdb for both errors and failures, and introduce a `--pdb-errors` to get the previous behavior.
Merge pull request #679 from Infinidat/374

Fix #374: "Older Versions" link broken on home page, and a few other issues.
fix suppressed deprecation warning

Python's default warning filter suppresses deprecation warnings;
Change the filter to make the warnings in nose.config visible.
Merge pull request #668 from Infinidat/388

Fix suppressed deprecation warning.
Merge pull request #688 from jszakmeister/fix-issue-687

Fix #687: verbosity is not a flag
Merge pull request #686 from jszakmeister/fix-issue-649

Fix #649: UnicodeDecodeError when an exception contains encoded strings
Merge pull request #684 from jszakmeister/fix-xunit-unicode

Fix xunit when writing unicode to stdout and stderr.
Fix #700: Tee is missing the writelines() method.