Preliminary alloc free support

[lmas]

Per #1

goos: linux
goarch: amd64
pkg: github.com/lmas/Damerau-Levenshtein
BenchmarkSimple-4   	   22352	     52824 ns/op	       4 B/op	       0 allocs/op
PASS
coverage: 94.6% of statements

@stapelberg this should be good enough right? ;)
It's not thread safe though and not so sure I want to add that too, feels a bit like over engineering.

[stapelberg]

@stapelberg this should be good enough right? ;)

Thanks for the change! I can confirm that this is a significant speed-up: my benchmark now completes in 40 seconds. For comparison, I tried running the same benchmark without this change, and cancelled it after it still did not complete in >6 minutes!

It's not thread safe though and not so sure I want to add that too, feels a bit like over engineering.

Agreed! Users will probably not mind adding goroutine safety if they need it.

[lmas]

Done and done, thanks man