[NEW] OID tests
[WIP] snmp extension - tree data structure
[WIP] update docs for oid tests
[UPDATE] MibTree logic
[FIX] Mib tree leaves start at 1, not 0.
[DOC] update readme a little
[REFACTOR] agentx -> snmptools as package name
[REFACTOR] Renaming methods and improving docs for snmpd extension code.