dt v0.0.9

New features

• add -resolver flag. Pick your own resolver
• add -json flag. Output results in json
• add -showfail flag. Only show checks that fail/warn

Improvements

• improve ETA guess using latency
• use cache if possible
• do a better job with wildcards (A/AAAA)
• use ipv6 only if available
• more debug output with -debug

Bugfix

• fix incorrect status in mxcheck