Setting author

[Guilhem BONNEFILLE <guilhem bonnefille gmail com>]

Hi,

I releaseD my set-author branch.

This topic branch consists of adding the ability to set an author for
the commit (different than the committer). This feature is really
useful, specially for project with many "minor" contributors: such
contributors only send only-patch and don't necessary use Git. In order
to keep track of contribution, it is needed to set a specific author.

Please, pull this branch.

A screenshot:
http://picasaweb.google.com/guilhem.bonnefille/CapturesDCran#5363243652017728450