Update links from `README.md`
Use 2 space indentation in `.travis.yml`
Make Travis CI limit the Git clone depth even more

In order to speed up the tests a little bit more, inform Travis
CI to limit the Git clone depth to 10 commits (default is 50).

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 e.g.:

    $ time g clone --depth 10 git@github.com:h5bp/html5boilerplate.com-mobile.git
    ...

    real    0m2.259s
    user    0m0.020s
    sys     0m0.016s

    $ time g clone --depth 50 git@github.com:h5bp/html5boilerplate.com-mobile.git
    ...

    real    0m2.700s
    user    0m0.032s
    sys     0m0.020s

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Ref: http://git-scm.com/docs/git-clone
     https://twitter.com/travisci/status/288390896339267584
Make Travis automatically update the server branch

Configure Travis to automatically update the content from
the branch¹ intended for the server by executing the
`update_server_branch.sh` script whenever the tests pass.

Note: The `update_server_branch.sh` script will only update
the content if the changes were made in the `master` branch.

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¹ https://github.com/h5bp/html5boilerplate.com/wiki