Small modifications for composer installation
Silly 'non-empty dir' removal attempt
relative path calculation of 'config' folder
Uncaught exception 'InvalidArgumentException' with message 'Identifier "session"...
resolves bolt/bolt#909
Merge remote-tracking branch 'remotes/myfork/issue909'

* remotes/myfork/issue909:
  Uncaught exception 'InvalidArgumentException' with message 'Identifier "session"... resolves bolt/bolt#909