discover sysObjectID

New column added to DB, users will need to delete DB or add the column:
% sqlite3 corona.db 'alter table devices add column oid_sysObjectID varchar(255)'

We need this to reliably recognize some devices (fortios)
closes #2
allow polling specific cidr from cli

[fisakytt@lan-login1 ~/.config/corona]% corona --help
Usage: corona [cidr]
    -d, --debug      Debugging on
    -h, --help       Display this help message.
[fisakytt@lan-login1 ~/.config/corona]% corona 100.64.255.228/32
ptr [cpe31.fi.cpe.tdc.net] sysName [cpe31.fi.cpe.tdc.net] ip [100.64.255.228]
[fisakytt@lan-login1 ~/.config/corona]%

Rationale is that you maybe just added node, you need it to be discovered right
now, so you can satisfy other dependencies, such as confiugration backups.
bump up gemspec version