v0.7.1

• License changed to permissive license (MIT).
• Added TestSuite - basic tests for actors
• Removed option OptUsingChan in favor of new option OptAsChan
• MailboxSender interface changed to improve comparability for remote communication.
  Interface changed from:

 type MailboxSender[T any] interface {
     SendC() chan<- T
 }

to:

 type MailboxSender[T any] interface {
     Send(ctx Context, msg T) error
 }