Do tagger copying with less iteration

This makes minimal difference to the benchmarks in cayley_test.go (a
variable ±5% on the bigger cases).
Fix error in REPL term shutdown leaving tty unsane

Previously we did not close the liner term unless a SIGINT or SIGKILL
was received. This left the terminal in raw. Fix that.
Quieten go vet in mongo
Merge pull request #131 from kortschak/tagger

Do tagger copying with less iteration
Merge pull request #132 from kortschak/repl

Fix error in REPL term shutdown leaving tty unsane
Merge pull request #135 from kortschak/mongo

Quieten go vet in mongo