{ :version "1.0.1"}

  {"1.0"{:from-version "1.0"
           :to-version "1.1.0"
           :migration-fns [identity]}

   "1.1"{:from-version "1.1"
           :to-version "1.2.0"
           :migration-fns [add-effects/add-pattern-effects]}}

  Functions used when handling migration of state, where state is represented by a Clojure map.

  The functions within the migration namespace can be categorised as:

|Function group|Functions|
|---|---|
|helper functions| [[major-version]], [[minor-version]], [[major-minor-version]], [[could-upgrade-version]]|
|migration interface| [[migrate-state]]|

  The migration functions assume the state map contains a version attribute

```clojure
  { :version "1.0.1"}
```

 Some functions require a migration map which for each current version defines the migrations that are defined
 to a later version.

```clojure
  {"1.0"{:from-version "1.0"
           :to-version "1.1.0"
           :migration-fns [identity]}

   "1.1"{:from-version "1.1"
           :to-version "1.2.0"
           :migration-fns [add-effects/add-pattern-effects]}}
```

The ```:migration-fns``` attribute is a vector of functions that accept the old state map and return a newly migrated state map.