Bugfix: reset allows custom initial value, loadAll updates currentIndex

[geoffdavis92]

What:

1. Add support for Floodgate#reset to explicitly pass new initial value to new Floodgate#queue generator
2. Fix Floodgate#loadAll not updating Floodgate#state.currentIndex

Why:

1. Floodgate's state locks up if its props are controlled by a parent, exportState is saved by that parent, and Floodgate is toggled between mounted instances in a "loadComplete === true" state
   • When mounting is toggled, exportState could save the currentIndex value which could then be mapped to the initial prop when re-mounted
   • This creates a situation where the initial value is equal to the length of the data prop's value, making the reset method useless
2. Mostly for testing purposes, but also to ensure a consistent experience between the load methods

How:

1. Adding the initial property to the Floodgate#reset method's parameter
   • Used in the initialization of a new Generator
   • When not specified, defaults to Floodgate#props.initial
2. Setting Floodgate#state.currentIndex to the length of Floodgate#data

Reference:

Closes #40
Closes #41