Release 1.2.1

[hainayanda]

• Added LockRunner protocol to abstract safe multithread access
• Change RetryControl closure into escaping
• Added Finally block
• Added Timeout
• Fix Aggregate not running first aggregated request
• Make some weak variable on closure strong, since in the real implementation, there's no one keeping the variable to be strong and the variable will always be released after the closure completed
• Fix retry control called when task is cancelled
• Remove some mutating to achieve more functional code, thus less effect to any outside variable
• Added some unit test for aggregate
• Added validate and retrycontrol to unit test
• Added unit test for decoder