cancel vs cancelAtPeriodEnd

As discussed in #20.
Spacing Fix

Added  space after the if statement.
Working on subscriptions.
Working on subscription shim.
Working on tests.
Update migration.
Fix signatures.
Fix params.
Working on customer creation.
Fix method calls.
Unify method names.
Fix retrieve.
Tweaking how things are updated.
Pull all subscriptions.
Fix data.
Working on subscriptions.
Cleaning up code.
Cleaning up more code.
Green up tests.