Update verision, make Nil/Cons internal

Author: dsyme

RELEASE_NOTES.md

@@ -1,5 +1,6 @@
-### 1.12.2 - 27.03.2015
+### 1.13 - 27.03.2015
 * Renamed to FSharp.Control.AsyncSeq
+* Remove surface area
 
 ### 1.12.1 - 27.03.2015
 * Added Async.bindChoice, Async.ParallelIgnore, AsyncSeq.zipWithAsync, AsyncSeq.zappAsync, AsyncSeq.threadStateAsync, AsyncSeq.merge, AsyncSeq.traverseOptionAsync, AsyncSeq.traverseChoiceAsync

src/FSharp.Control.AsyncSeq/AsyncSeq.fs

@@ -19,7 +19,8 @@ type AsyncSeq<'T> = Async<AsyncSeqInner<'T>>
 
 /// The interanl type that represents a value returned as a result of
 /// evaluating a step of an asynchronous sequence
-and AsyncSeqInner<'T> =
+and AsyncSeqInner<'T> = 
+    internal
     | Nil
     | Cons of 'T * AsyncSeq<'T>