Explain how to install Sphinx with pip (rather than easy_install). Fixes #1447

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branch : hickford/explain-how-to-install-sphinx-with-pip-r-1410714824122
Merged in hickford/sphinx/hickford/explain-how-to-install-sphinx-with-pip-r-1410714824122 (pull request #286)

Explain how to install Sphinx with pip (rather than easy_install). Fixes #1447