Leverage babel-plugin-minify-dead-code-elimination

[mixonic]

#180 introduces https://github.com/chadhietala/babel-plugin-debug-macros for feature flagging. This library will translate feature flags to true false literals, however it will not strip dead code paths.

This project should strip dead code via https://github.com/babel/babili/tree/master/packages/babel-plugin-minify-dead-code-elimination in a manner similar to @chadhietala's PR to Ember: emberjs/ember.js#15043

[rwjblue]

We've removed the feature flagging for MU, so this is no longer an issue.