Replace `ocramius/instantiator` with `doctrine/instantiator`.

Refs: Ocramius/Instantiator#13
Flesh out the stubs and mocks documentation
Merge pull request #434 from richardmiller/add-to-stubs-docs

Flesh out the stubs and mocks documentation
Merge pull request #431 from whatthejeff/doctrine-instantiator

Replace `ocramius/instantiator` with `doctrine/instantiator`.
Simplify some language in the docs and move to use 2nd person consitently

Conflicts:
	docs/manual/installation.rst