Fix for linked account information bug

Somtimes linked accounts were being displayed incorrectly.

The seralisation code has been updated to fix this with both Mongo DB and NeDB (used when no Mongo DB is configured).

NextAuth also has an update to it’s error handling to reduce future errors so have updated the dependancy.

Dropdown and nav menu toggle improvements

Partly addresses issues in iaincollins#57

* Dropdown menus in the nav menu on mobile now display correctly.
* The nav menu no longer requires JavaScript to be enabled to work and uses a pure CSS solution. I may prototype to extend this to other components and see if it’s a pull request the Reactstrap folks would be interested in.

Upgrading to Next.js 2.0 release version (from beta)

This is an overdue update as it came out as release a few weeks ago now. The beta version of 2.0 we were tracking was a late canidate so there are no actual code changes.

Fixes iaincollins#10 (Session handling bug)

* Session state now updates correctly after sign in on all browsers, including Interent Explorer.

* The most important element of the fix was adding componentDidMount() call to update session data in auth/signin page (as it’s the oauth callback page).

Changes to simply the flow in recent refactoring made this easier to fix.

Update README.md

Refactored auth option handling with ES6 params

This makes it much clearer what the method options are, what options are being passed and removes the amount of code required.

Also improved error handling on startup.

Now silently revalidates sessions periodically

This resolves issue iaincollins#6.

The client how checks 'clientMaxAge', which is set on the server (along side all the other session options) and uses that value to determine if it it should fetch the session data from the server or from the cache on disk.

Note that the cache on disk is shared between tabs, so logging you out on one will cause you also to be logged out on the other pages when you next interact with the site regardless.

This option just ensures the client will never stray too far from the data on the server (e.g. in the event a users session information is updated or forceably expired on the server).