Fixes and improvements

Changes:

 aa5216d (Ernesto Jiménez, 28 seconds ago)
    Reset nagging when user no longer has details

 d4113d1 (Ernesto Jiménez, 3 minutes ago)
    Whois improvements

      * hubot replies to the person asking
     * Check if a user exits when in doubt
     * Remove the exists flag if a user used to have info but no longer does

 7bb395a (Ernesto Jiménez, 15 minutes ago)
    Don't process whois messages unless HUBOT_WHOIS_SP is defined

 608077a (Ernesto Jiménez, 16 minutes ago)
    Fix bug where we did not get the name