Deserialized sessions should create a get-alphas-fn if provided

[WilliamParker]

In the non-serialization path the :get-alphas-fn is created in the compiler. [1, 2] When clara.rules.engine/assemble is called it expects a user-provided get-alphas-fn to be wrapped already. [3] The durability namespace calls through to the wrapper functionality when it uses the default get-alphas-fn [4, 5] but it does not wrap a user-provider get-alphas-fn. The user would need to use the private create-get-alphas-fn in the compiler to provide a working custom get-alphas-fn. Otherwise Clara would call a user-provided function directly expecting it to return alpha nodes, which it wouldn't do. The way Clara uses the user-provided function to create a get-alphas-fn is an internal implementation detail that should not be exposed in this way.

1. https://github.com/rbrush/clara-rules/blob/0.13.0-RC2/src/main/clojure/clara/rules/compiler.clj#L1639
2. https://github.com/rbrush/clara-rules/blob/0.13.0-RC2/src/main/clojure/clara/rules/compiler.clj#L1530
3. https://github.com/rbrush/clara-rules/blob/0.13.0-RC2/src/main/clojure/clara/rules/engine.cljc#L1569
4. https://github.com/rbrush/clara-rules/blob/master/src/main/clojure/clara/rules/durability.clj#L433
5. https://github.com/rbrush/clara-rules/blob/master/src/main/clojure/clara/rules/durability.clj#L404

[mrrodriguez]

I'll just fix this in the #228

It's highly related to changes there anyways.

[WilliamParker]

Closing since this was fixed by @mrrodriguez in https://github.com/rbrush/clara-rules/pull/228/files