update encryptionKey to secret in bogart.session and CookieDataProvider
make batteries require a secret
improve invalid response object error message
Merge pull request #88 from weskinner/master

improve invalid response object error message
add session#destroy method to remove a session
bump to v0.5.16
Merge branch 'master' into develop

Conflicts:
	lib/middleware.js
	lib/middleware/session/session.js
	package.json
	spec/middlewareSpec.coffee
remove an unneeded return in Facebook middleware's parse