Add GitShellIntegration - shell based git support

This class simply uses the git command and no longer requires any git
python bindings to be around. It is very useful as everyone using git
has git installed but may not have python-git (or python3 support for
python-git) installed.

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>
Fix PEP8 issues

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>
Bump copyright for 2012-2014

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>
Add __all__ to versiontools

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>
Add bzr shell integration

This patch adds a way to use versiontools with bzr without having to
import it in python2.x codebase. This is especially useful when working
in python3 where that is simply impossible but it is also useful for
Windows users that typically don't have bzr in their PYTHONPATH but can
have the command line tool in PATH.

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>
Update changelog

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>
Handle OSError in shell integration

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>
Fix python-git code not to shadow a variable
Fix various PEP8 issues
Fix tests for python3.3
Stop supporting << python2.6, support up to 3.3

This patch marks python2.4, python2.5 as unsupported while marking
python3.2 and python3.3 as supported.

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>