Avoid multiple babel-polyfill loaded

[logankoester]

An error is thrown if a process attempts to load babel-polyfill more than once:

ERROR in only one instance of babel-polyfill is allowed.

See shakacode/bootstrap-loader#16

[clayne11]

This is actually not the right approach. A library should never provide the babel-polyfill at all. It can cause certain runtime environments to break such as Meteor.

This will emulate a full ES2015 environment and is intended to be used in an application rather than a library/tool.

(emphasis mine)

See https://babeljs.io/docs/usage/polyfill/

[aldeed]

I agree we should remove the dependency. I can't remember what it was needed for, so might need to keep it as a peer dependency or rewrite whatever code relies on it.

[aldeed]

Removed this dependency in 29c6d9f