When called with an already persisted entity, Lotus::Repository#persist does not return the entity

When calling Lotus::Repository#persist with a persisted entity, the return value is not that entity.

For the SqlAdapter the value ```1``` is always returned.

For the MemoryAdapter a hash of the entity's attributes is returned.

Test output below:

```
  1) Failure:
Lotus::Repository::with sql adapter::.persist::when passed a persisted entity#test_0001_should return that entity [/Users/benaskins/Development/lotus_model/test/repository_test.rb:48]:
--- expected
+++ actual
@@ -1 +1 @@
-#<User:0xXXXXXX @id=65, @name="S", @age=nil>
+1

  2) Failure:
Lotus::Repository::with memory adapter::.persist::when passed a persisted entity#test_0001_should return that entity [/Users/benaskins/Development/lotus_model/test/repository_test.rb:48]:
--- expected
+++ actual
@@ -1 +1 @@
-#<User:0xXXXXXX @id=1, @name="S", @age=nil>
+{:id=>1, :name=>"S", :age=>nil}
```

Before I attempt to write a patch, can you confirm whether or not this is expected behaviour?