get-zones output should work as input into preview (#688)

* Add tests for get-zones
* fix CAA, SSHFP, TLSA and other bugs
* New format for get-zones: "djs" which is js but uses "disco commas"
* Print diffs using github.com/andreyvit/diff

Co-authored-by: Tom Limoncelli <tlimoncelli@stackoverflow.com>

vendor/github.com/andreyvit/diff/trim.go

@@ -0,0 +1,19 @@
+package diff
+
+import (
+	"strings"
+)
+
+// TrimLines applies TrimSpace to each string in the given array.
+func TrimLines(input []string) []string {
+	result := make([]string, 0, len(input))
+	for _, el := range input {
+		result = append(result, strings.TrimSpace(el))
+	}
+	return result
+}
+
+// TrimLinesInString applies TrimSpace to each line in the given string, and returns the new trimmed string. Empty lines are not removed.
+func TrimLinesInString(input string) string {
+	return strings.Join(TrimLines(strings.Split(strings.TrimSpace(input), "\n")), "\n")
+}