Add .gitreview configuration for git-review

For use with git-review[1]. After installing git-review and this patch,
you can start development with:

    git clone https://gerrit-ring.savoirfairelinux.com/sflphone
    cd sflphone
    git review -s

This will add the pre-commit hook as well. The next thing you could do
is setting a ssh remote for pushing to avoid having to store a http
password (advantage of this is that you do not need to unlock your SSH
key just for pulling new changes):

    git remote set-url origin --push \
        ssh://username@gerrit-ring.savoirfairelinux.com:29420/sflphone.git

 [1]: https://pypi.python.org/pypi/git-review

Change-Id: I8b3e41c93d2d647ca81f805b619b44ac8997dc95

.gitreview

+[gerrit]
+host=gerrit-ring.savoirfairelinux.com
+port=29420
+project=sflphone.git
+defaultremote=origin
+defaultbranch=master