Version 1.5.0 release branch

**Additions/Non-Breaking Changes**

* You can add stores and actions to existing Flux instances via `addStore`, `addStores`, `addAction`, and `addActions` (#68, #71, #77)
* `Flux` instances are now EventEmitters, and emit a `"dispatch"` event (with `type` and `payload` arguments) when an action calls `this.dispatch(type, payload)`, useful for cross-cutting concerns like logging
* `Store#bindActions` now takes a hash (similar to the static `actions` hash) in addition to an argument list (#51, #78)
* Fluxxor will throw more descriptive errors in many situations that are obviously incorrect (for example, when an action handler is not defined, or an action type in `bindActions` is falsy)

**Deprecations**

`Fluxxor.FluxChildMixin` is now deprecated; instead, use `FluxMixin` anywhere you want access to `getFlux()` (#59)