assaf/vanity — pull request #234 by phillbaker (2014-10-16 01:46:55+00:00)
Title: Ensure that metric hooks are added idempotently.

This also removed the deprecated Playground#define method as it contributes to the confusion.

This should close #232.

- [ ] Needs to ensure that it still can add multiple hooks in the case of two simultaneous experiments using the same metric.