Stacked effects

Added support of so called "stacked" effects. Before if during one transition two or more actions issued the same effect (effect with the same key) only the last one would be executed. Now all of them will be executed. The order of execution should be considered to be undetermined for now.

Shared isolation

Multiple interpreters are allowed to share the same isolated re-frame db part.

Keywordized state 2

State keywordization function haven't been tested properly and was buggy, now it's fixed.

Keywordized state

Interpreter state is now (js->clj) converted (with keys keywordized) before being stored into re-frame db.

Let machine

Two new macros has been added let-machine and let-machine-> to help dynamically define a machine

Activities support

The re-state interpreter now handles XState activities