Update S2InitTwitter.groovy

s2-init-twitter results configs on Config.groovy:
- grails.plugins.springsecurity.twitter.app.consumerKey
- grails.plugins.springsecurity.twitter.app.consumerSecret
and causes "401 Unauthorized" by "Connect with Twitter" button.
the document says:
- grails.plugins.springsecurity.twitter.consumerKey
- grails.plugins.springsecurity.twitter.consumerSecret
Merge pull request #13 from sudoyu/patch-2

Update S2InitTwitter.groovy (credentials)