Custom exceptions for every feature, delay for waiting responses

[Bestfootballer]

Hi, I added custom exceptions for every feature you have implemented, in order to have specific errors if someone has to do something when catches these exceptions.
I also added a new variable into FTPConnect and FTPSocket classes called "sendingResponseDelay" for customizing the delay between the responses coming from FTP SERVER.

I did these changes cause I'm currently develop a desktop app that uses your package and in some points, I needed custom exceptions in order to do custom actions in the catch block. Then, I added the delay for reducing the time between responses in order to have results faster.
Finally, I updated the tests in order to work with the new exceptions.

I hope you'll enjoy my work

Waiting answers.
Have a nice day :)
Antonio