Merge pull request #179 from multiformats/fix-godoc

The comment on GetHasher was copy-pasta and referred to Registry.

registry.go

@@ -18,7 +18,7 @@ func Register(indicator uint64, hasherFactory func() hash.Hash) {
 	mhreg.Register(indicator, hasherFactory)
 }
 
-// Register is an alias for Register in the core package.
+// GetHasher is an alias for GetHasher in the core package.
 //
 // Consider using the core package instead of this multihash package;
 // that package does not introduce transitive dependencies except for those you opt into,