…reduxjs#1569)

* throw error if getState, subscribe, or unsubscribe called while dispatching

* prevent throwing if not subscribed

* update getState error message

* fix space after period

* update subscribe/unsubscribe error messages

* Add a doc section on dispatching during middleware setup.

* Warn when dispatching during middleware setup.

* Upgrade the warning to an error.

* Update docs to match thrown error behavior.

* Add mapped type for combineReducers in index.d.ts

Updated typescript to 2.1.4
Updated typescript-definition-tester to 0.0.5
Updated typescript tests to use proper import
Added mapped type to index.d.ts

* add strict null check for reducer

Updated Reducer<S> type in index.d.ts
Add strictNullChecks flag to typescript spec

Behavior has been replaced with the "it warns when dispatching during middleware setup" test in the 'next' branch.

* Revamp TypeScript typing with more type safety

* Provide a default action type for combineReducers

* Change state default types to any

* Don't parameterize Dispatch with a state type

* Remove docstring about excised type parameter