added autoClose to Navbar props

## Problem:
Bootstrap allows for a class ( **in** ) to be added to **Nav**, causing **Nav** to collapse. Can be used with props.onToggle(). react-bootstrap introduces a new state ( **navOpen** ) that is hidden from props.onToggle() and prevents the optional bootstrap functionality.

## Current functionality:
With **Nav** open,
click on **NavItem**,
must click on **toggleButton** to close.

## Change:
With **Nav** open,
click on **NavItem**,
Nav closes automatically.

### default:
autoClose: true

#### Notes:
In Bootstrap, adding class ( **in** ) to Nav causes an abrupt closure which must be dealt with in further code. This solution elegantly causes Nav to close with the same animation that it opened with.