magit-revert-buffers: don't use auto-revert-handler

`auto-revert-handler' does quite a few things we don't need, so instead
of using that just call `revert-buffer', `vc-find-file-hook' directly.

Backport of edf2b42ec6c1309402e62e3b307e1656c8f38680.
travis-ci: use generic

See https://github.com/travis-ci/travis-ci/issues/1201.
README.md: fix tarball url
magit-revert-buffers: "reverts" all file-visiting buffers again

This is a temporary kludge, on next I have to find a better solution.
See #1546.
magit-revert-buffers: compare truenames

See #1545.