Merge pull request #170 from guestisp/master

Pull request to sync the code
Merge pull request #171 from guestisp/master

Pull request to sync the code
Merge pull request #172 from guestisp/master

Pull request to sync the code
Merge pull request #173 from guestisp/master

Pull request to sync the code
Merge branch 'shineisp/sandbox'
Added garbage collector to OAuth2
Overwrite invoice when payment is done.