Added "@" and "." to userID acceptable chars
Forgot to add "-" to userID acceptable chars
modified user verification
as mentioned by paulocmguerreiro removed echo "hi" from random()

I think this piece of code was added during testing and never removed.
Update Sessions Last_Activity when using existingSession() or data is
requested/set.
Updates readme
Updated the expired session removal script

Expired session are removed when new sessions are created. This would result in timely removal of expired session making database less burdened
code to remove expired sessions 

minor coding style fix
minor coding style fix
Adds build status badge to `README.md`