Use alternative factory_girl callback syntax

factory_girl's `before` and `after` callback methods appear to confuse
Transpec dynamic code analysis:

    /Users/alexbcoles/.gem/ruby/2.1.1/gems/factory_girl-4.2.0/lib/factory_girl/definition_proxy.rb:35:in `add_attribute': wrong number of arguments (5 for 1..2) (ArgumentError)
    	from /Users/alexbcoles/.gem/ruby/2.1.1/gems/factory_girl-4.2.0/lib/factory_girl/definition_proxy.rb:89:in `method_missing'

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Convert specs to RSpec 2.99.0 syntax with Transpec

This conversion is done by Transpec 1.12.0 with the following command:
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* 100 conversions
    from: it { should ... }
      to: it { is_expected.to ... }

* 17 conversions
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      to: expect(collection.size).to eq(n)

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      to: expect(obj).to

* 4 conversions
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      to: allow_any_instance_of(Klass).to receive(:message)

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      to: skip 'is an example' { }

* 1 conversion
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      to: expect(collection.size).to be >= n

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