remove duplicated if in spec

                   
|Q            |A  |
|---          |---|
|Bug Fix?     |n  |
|New Feature? |n  |
|BC Breaks?   |n  |
|Deprecations?|n  |
|Tests Pass?  |n  |
|Fixed Tickets|   |
|License      |MIT|
|Doc PR       |   |
                   


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@ciaranmcnulty this is cleaning a bit the config to run ``composer install`` in the ``install`` section, to be forward-compatible (Travis is preparing first-class composer support like they do for bundler in Ruby, and this will avoid running composer twice, first in ``install`` and then in ``before_script``.

however, there is 2 mistakes in this PR:

- it should indeed be submitted on its own instead of being included in an unrelated PR
- configuring the php.ini for HHVM should not be done in the ``install`` section, as this would not be forward-compatible for the day where we will want to just remove the ``install`` section in favor of the default Travis config for PHP