dummy object creation without conditionals

This is an implementation of Ian's comment, found here https://github.com/edx/edx-platform/pull/65#issuecomment-19172768.

Pulling the first line of the Segment.io snippet outside of the `if` statement allows it to serve as its own dummy object, and cover all of Segment.io's methods. Leaving the `analytics.load` line inside the `if` statement will only load it when an API key is available.