Add snippet for Google Optimizely (fixes #70)

[hollomancer]

Description of changes

Adds Google Optimizely snippet, though I'm not sure if it's in the right place, and it's annoying to test. Would like someone who originally added ReactGA to verify.

Issue Resolved

Fixes #70

[kylemh]

@alexspence is the man on this one. @rickr any safe way to test these 3rd-party integrations?

[rickr]

Looks like you can set your NODE_ENV to production and run a build to test this out.

[Cooperbuilt]

Are we still interested in google optimizely?

[kylemh]

@hollomancer ^

[hollomancer]

Yeah, we are - I just haven't had time to look at this. If anyone else is able to jump in, please grab it. If not, I can close

[kylemh]

https://docs.travis-ci.com/user/environment-variables/

Whoever has access to Travis can implement this with @rickr 's suggestion.

[JennWeideman]

@hollomancer @Cooperbuilt @kylemh status after last nights talk?

[kylemh]

@JennWeideman I vaguely remember discussing AB testing frameworks... I don't have a decision on what's best, but there's a lot to do before we need to decide. I'm going to close this PR and we can continue discussion via #70