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Properly align checkboxes according to bootstrap

Before:

![Screenshot_2015-06-10_17.01.26](https://gitlab.com/gitlab-org/gitlab-ce/uploads/2e874cc0a6edd52d98a17030f3d16f24/Screenshot_2015-06-10_17.01.26.png)

After:

![Screenshot_2015-06-10_16.59.31](https://gitlab.com/gitlab-org/gitlab-ce/uploads/7d91ffe8e981f9bc57d9a18ce8ac79e2/Screenshot_2015-06-10_16.59.31.png)
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

See merge request !793