js_test.go should generate & test zonefile output too (#986)

* js_test.go: Do a zonefile test if $TESTNAME/parse_tests/{zonefile} exists.
* Add parse_tests zone files for all the tests that make sense.
* js_test.go: Addd the test datafile when displaying failures.
* 007-importTransformTTL.js: Was referring to a non-existent domain.
* 012-duration.js: Had duplicate DNS records.
* 029-dextendsub.js: Move CF-related tests to separate test.
* validate.go: Report non-existent domains as an error.
* cloudflareProvider.go: newCloudflare should not talk to the API.

pkg/js/parse_tests/036-dextendcf.js

@@ -0,0 +1,10 @@
+var REG = NewRegistrar("Third-Party", "NONE");
+var CF = NewDnsProvider("Cloudflare", "CLOUDFLAREAPI");
+
+D("foo.com", REG, DnsProvider(CF));
+D_EXTEND("sub.foo.com",
+    A("test1.foo.com","10.2.3.1"),
+    A("test2.foo.com","10.2.3.2"),
+    CF_REDIRECT("test1.foo.com","https://goo.com/$1"),
+    CF_TEMP_REDIRECT("test2.foo.com","https://goo.com/$1")
+);