Install Omniauth
Install omniauth-twitter

You lied to us, RailsCasts! You lied!

Specifically, http://asciicasts.com/episodes/235-omniauth-part-1 lied to
us about which gem we needed to install. See also
https://github.com/intridea/omniauth/issues/641 for the issues this
caused.
Gitignore the local credentials.sh script.

This contains API keys and secrets and so should not be kept in Git.

Example script (edit as required):

export MANDRILL_USERNAME=xxxxxxxxxxxxxxxxxxxxx
export MANDRILL_APIKEY=xxxxxxxxxxxxxxxxxxxxx
export TWITTER_KEY=xxxxxxxxxxxxxxxxxxxxx
export TWITTER_SECRET=xxxxxxxxxxxxxxxxxxxxx
Added an Authentications table.

Connects users to remote web services, as recommended at
http://asciicasts.com/episodes/235-omniauth-part-1

In addition, we store "token" and "secret" fields.
Stub "authentications#create" method.
Removed unneeded generated files.
Add omniauth to our middleware.
Fix typo in models/member.rb
Fix stub authentications#create method

As per comment at
http://railscasts.com/episodes/235-omniauth-part-1?view=comments#comment_153390
Create an authentication object on successful callback.
Store token on creating a new authentication.
Added authbuttons-rails gem

Provides pretty icons for Twitter, FB, GitHub, etc. No Flickr :-(
Restrict ability to create authentications.
Only show current member's authentications on index.
Add a "name" column to authentications.
Remove unused methods on authentications.
Add "link to another account" link to authentications/index
Store name with authentications
Make the authentication into a link to your Twitter page.

When we support other authentication providers, we'll need to make this
into a callback or something.
Delete specs for unused views and controller methods.