Make dialyzer happy (#32)

* Update a couple of type specs to match reality
* Remove dead code
diff --git a/src/erlfdb_directory.erl b/src/erlfdb_directory.erl
index d727ad3..22966af 100644
--- a/src/erlfdb_directory.erl
+++ b/src/erlfdb_directory.erl
@@ -461,9 +461,6 @@
     end.
 
 
-create_or_open_int(TxObj, Node, {}, Layer) ->
-    create_or_open_int(TxObj, Node, [], Layer);
-
 create_or_open_int(_TxObj, Node, [], LayerIn) ->
     Layer = case LayerIn of
         <<>> -> <<>>;
diff --git a/src/erlfdb_nif.erl b/src/erlfdb_nif.erl
index 9e25520..b281a4f 100644
--- a/src/erlfdb_nif.erl
+++ b/src/erlfdb_nif.erl
@@ -248,8 +248,7 @@
     erlfdb_database_set_option(Db, Opt, BinVal).
 
 
--spec database_create_transaction(database()) ->
-        {ok, transaction()}.
+-spec database_create_transaction(database()) -> transaction().
 database_create_transaction({erlfdb_database, Db}) ->
     erlfdb_database_create_transaction(Db).
 
@@ -309,7 +308,7 @@
         StreamingMode::streaming_mode(),
         Iteration::non_neg_integer(),
         Snapshot::boolean(),
-        Reverse::boolean()
+        Reverse::integer()
     ) -> future().
 transaction_get_range(
         {erlfdb_transaction, Tx},