Fix for a circular reference issue

[ericlu88]

Right now there's a circular reference path in our code base:

lib/interface.ts->
lib/apisession/session.ts->
lib/subscription/subscription.ts->
lib/util/historical-buffer-manager.ts->
lib/interface.ts

Will have to remove this circular reference problem.

[ericlu88]

Dependency map as of right now. Noticed the circular reference path.