* Add SSHFP record support
Use offset since we may receive a full dns packet
Account for maximum hash lengths for each hash type
fix: don't use the output of `Buffer#copy()`, instead use `Buffer#byteLength`
fix: normalize fingerprint string
fix: the offset pointer starts out at RDLENGTH
fix: account for the `RDLENGTH` field in `rsshfp.decode()`
* tests: add test for the SSHFP record type
