Fix replication spec

Don't rely on serialization to handle modifications after documents are
connected.

spec/text-buffer-replication-spec.coffee

@@ -5,7 +5,6 @@ describe "TextBuffer replication", ->
 
   beforeEach ->
     buffer1 = project.buildBufferSync('sample.js')
-    buffer1.insert([0, 0], 'changed\n')
     doc1 = buffer1.getState()
     doc2 = doc1.clone(new Site(2))
     doc1.connect(doc2)
@@ -14,6 +13,9 @@ describe "TextBuffer replication", ->
     waitsFor ->
       buffer1.loaded and buffer2.loaded
 
+    runs ->
+      buffer1.insert([0, 0], 'changed\n')
+
   afterEach ->
     buffer1.destroy()
     buffer2.destroy()