Remove global app variable

[Tbruno25]

Currently a singleton can_explorer.app.app is created on import and referenced as a global variable. This leads to false failures and potential strange behavior when testing as experienced in #28.

A better design pattern should be utilized and all global references removed. d3c50b6 should also be reverted as it's a temporary fix to avoid the behavior.

[Tbruno25]

Global variables removed as part of #31 however the false failures remain.

#32 opened to track.