update README

README.md

@@ -6,19 +6,19 @@ This is the Coq development accompanying lambda-Rust.
 
 This version is known to compile with:
 
- - Coq 8.6
+ - Coq 8.6.1
  - Ssreflect 1.6.1
  - A development version of [Iris](https://gitlab.mpi-sws.org/FP/iris-coq/)
 
 The easiest way to install the correct versions of the dependencies is through
-opam.  Coq packages are available on the coq-released repository, set up by the
-command:
+opam.  You will need the Coq and Iris opam repositories:
 
     opam repo add coq-released https://coq.inria.fr/opam/released
+    opam repo add iris-dev https://gitlab.mpi-sws.org/FP/opam-dev.git
 
-Once you got opam set up, just run `make build-dep` to install the right
-versions of the dependencies.  When the dependencies change, just run `make
-build-dep` again.
+Once you got opam set up, run `make build-dep` to install the right versions
+of the dependencies.  When the dependencies change, just run `make build-dep`
+again.
 
 ## Building Instructions