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

@@ -1,10 +1,7 @@
-package wallet
+package revocation
 
 import "github.com/btcsuite/btcd/wire"
 
-// TODO(roasbeef): port Rusty's hash-chain stuff
-//  * or just use HD chains based off of CodeShark's proposal?
-
 // chainFragment...
 type chainFragment struct {
 	index uint64
@@ -21,6 +18,7 @@ type ShaChain struct {
 // NewShaChain...
 func NewShaChain(seed wire.ShaHash) *ShaChain {
 	// TODO(roasbeef): from/to or static size?
+	return nil
 }
 
 // NextHash...

revocation/shachain_test.go

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

wallet/shachain/hash_chain_test.go

@@ -1 +0,0 @@
-package wallet