WIP: decouple selenium install from travis

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This commit was sponsored by The Hoodie Firm.
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This commit was sponsored by The Hoodie Firm.
You can hire The Hoodie Firm:
http://go.hood.ie/thehoodiefirm

* * *

This commit was sponsored by The Hoodie Firm.
You can hire The Hoodie Firm:
http://go.hood.ie/thehoodiefirm