Add Social Login support

[typerandom]

Add support for social login with the SocialLoginLink and SocialLoginButton components.

Note

This depends on stormpath/express-stormpath#374 in order for Facebook to be supported.

How to verify

1. Checkout this branch.
2. Build it ($ npm run build).
3. Link it ($ npm link).
4. Checkout the social-login branch of the React example app.
5. Link to our React SDK feature branch ($ npm link react-stormpath).
6. Log into the Stormpath Console and configure/map the Facebook, Google, Github and LinkedIn social provider directories for your application.
7. Start the application ($ npm start).
8. Navigate to /login.
9. Verify that all of the mapped social providers are visible below a box called Or login with....
10. Click each provider and verify that you can login with them. Note that for Facebook, you need to patch the example application with the branch of this express-stormpath PR. Or else it won't work.
11. Login to the Stormpath Console, and unmap one provider at a time while restarting the app and verifying that they are removed from the Or login with... box.
12. When all providers are unmapped, verify that the Or login with... box disappears.
13. Using the documentation, open up the example application and manually add your own SocialLoginLink and SocialLoginButton.
14. Verify that the link/button works as expected.

Fixes #14.

[timothyej]

Don't forget to add Font Awesome to the example project :)

[typerandom]

It's actually added, didn't you try it with the social-login branch? :)
https://github.com/stormpath/stormpath-express-react-example/tree/social-login/build/fonts

[timothyej]

In the AngularJS SDK we've also displaying the buttons on the registrations form, but you are only showing it on the login form.

And also, the AngularJS SDK have colored buttons, while yours are just white.

What's your thoughts on that?

[timothyej]

Renders a link that can be used to sign into a social provider.

The user doesn't sign in to a social provider, so it should probably be more like this:

Renders a link that can be used to sign in using a social provider.

[timothyej]

Other than my comments this is really nice! 👍

[typerandom]

@timothyej I personally see the social login buttons on the signup page as an anti pattern. But I'll add it for consistency. I personally don't think that the colors add much value, so I just decided to go without styling them in the first version. It can be added in a later version.

[timothyej]

I personally see the social login buttons on the signup page as an anti pattern.

As a user I would never click on Login if I wouldn't already have an account, I would always click on Signup. But in this case I would not be able to signup with e.g. Facebook because that button would only be on the login page.

[typerandom]

@timothyej Comments have been fixed. Please review again :)

[timothyej]

You probably don't have to set className explicitly since you include all the properties using {...this.props}?

[typerandom]

Good catch. Will fix that! :)

[timothyej]

I've verified that everything works as expected :) I will merge this once you've fixed my comment.

[typerandom]

Sweeeet! :)

[typerandom]

@timothyej This is now fixed.