Update install instructions in README.rst
Update install instructions in README.rst

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andreabedini/PyTables,rabernat/PyTables,rabernat/PyTables,andreabedini/PyTables,avalentino/PyTables,andreabedini/PyTables,FrancescAlted/PyTables,PyTables/PyTables,FrancescAlted/PyTables,PyTables/PyTables,rabernat/PyTables,FrancescAlted/PyTables,avalentino/PyTables,andreabedini/PyTables,avalentino/PyTables,PyTables/PyTables,rabernat/PyTables