Corrected repo URL in README

Replaced nemesisdesign with ninuxorg
Some missing casts fixed in snmmp.AirOS backend
interfaces_type property + test added in snmp.AirOS backend
 * returns the interface type (e.g Ethernet, loopback);
 * modifications in interfaces_to_dict to include it
Improvements to soundness in snmp.AirOS backend #29

Modification in interfaces_mtu in snmp.AirOS backend according to #29

Modification in get_interfaces() in snmp.AirOS backend according to #29

Modification in interfaces_state in snmp.AirOS backend according to #29

Modification in interfaces_speed in snmp.AirOS backend according to #29

Modification in interfaces_bytes in snmp.AirOS backend according to #29

Modification in interfaces_MAC in snmp.AirOS backend according to #29

Modification in interfaces_type in snmp.AirOS backend according to #29
snmp.OpenWRT: use infinite while loop to avoid mismatch
snmp: added temporary debug info