README.md in lhm-1.2.0 vs README.md in lhm-1.3.0

@@ -50,9 +50,14 @@
 1.2 (dm-mysql-adapter).
 
 Lhm also works with dm-master-slave-adapter, it'll bind to the master before
 running the migrations.
 
+## Limitations
+
+Lhm requires a monotonically increasing numeric Primary Key on the table, due to how
+the Chunker works.
+
 ## Installation
 
 Install it via `gem install lhm` or add `gem "lhm"` to your Gemfile.
 
 ## Usage