Rename simple_https to simple_http and add minimal interface implementation

acme/dns_challenge.go

@@ -0,0 +1 @@
+package acme

acme/dvsni_challenge.go

@@ -1 +1,11 @@
 package acme
+
+type dvsniChallenge struct{}
+
+func (s *dvsniChallenge) CanSolve() bool {
+	return false
+}
+
+func (s *dvsniChallenge) Solve() {
+
+}

acme/simple_http_challenge.go

@@ -0,0 +1,11 @@
+package acme
+
+type simpleHTTPChallenge struct{}
+
+func (s *simpleHTTPChallenge) CanSolve() bool {
+	return true
+}
+
+func (s *simpleHTTPChallenge) Solve() {
+
+}

acme/simple_https_challenge.go

@@ -1 +0,0 @@
-package acme