Update sftp.conf.erb

Added SFTPRekey directive to virtualhost sftp config
Update sftp.pp

SFTPRekey directive syntax is:
SFTPRekey "none"|"required" [[interval bytes] timeout]
Update sftp.pp

Added TimeoutIdle proftpd directive
Update sftp.conf.erb

Added TimeoutIdle proftpd directive
Update sftp.pp

Made fail message clearer
Update sftp.pp

manifests/instance/sftp.pp:24:2sp_soft_tabs:ERROR:two-space soft tabs not used
Merge pull request #13 from bkkrp/master

Added SFTPRekey proftpd mod_sftp directive