usage enhancement: obsolete the sshuserconfig call

 - updated README to document the new behavior
 - TODO: integration tests once #6 is solved
 - refs #2
fix integration: sshuserconfig call became obsolete
add regression test for duplicate resource error

enhance test framework to test cases with ONE and TWO
sshuserconfig::remotehost with the same unix user
use stdlib ensure_resource helper

 - remove virtual resources entirely
 - require stblib
restore backwards compatbility
simplify tests in order to make it more readable
clarify README
Merge pull request #7 from Jimdo/obsolete_call_to_sshuserconfig

usage enhancement: obsolete the sshuserconfig call