Create skeleton for revocation methods

* Just rusty’s shachain for now

revocation/revocation.go

@@ -0,0 +1,10 @@
+package revocation
+
+// TODO(roasbeef):
+//  * fin..later
+//  * reg HD Chain
+//  * Codeshark's sub-branch proposal
+//  * Rusty's hypercube shachain
+//  * more...idk?
+type VerifiableRevocation interface {
+}

revocation/shachain.go

@@ -0,0 +1,30 @@
+package revocation
+
+import "github.com/btcsuite/btcd/wire"
+
+// chainFragment...
+type chainFragment struct {
+	index uint64
+	hash  wire.ShaHash
+}
+
+// ShaChain...
+type ShaChain struct {
+	lastChainIndex uint64
+
+	chainFragments []chainFragment
+}
+
+// NewShaChain...
+func NewShaChain(seed wire.ShaHash) *ShaChain {
+	// TODO(roasbeef): from/to or static size?
+	return nil
+}
+
+// NextHash...
+func (s *ShaChain) NextHash() {
+}
+
+// GetHash...
+func (s *ShaChain) GetHash(index uint64) {
+}

revocation/shachain_test.go

@@ -0,0 +1 @@
+package revocation