rails_util.rb: don't delete facebook cookie (historical reason)
rails_util.rb: adopt changes from rest-more, see:

https://github.com/cardinalblue/rest-more/commit/101e4b25f11e4cf3713fa2f1d6b5a46982266e44
https://github.com/cardinalblue/rest-more/commit/0e7d4db588ecc287fd8b2840c880dfb3fe3c3096
.travis.yml: test against 2.0 and remove 1.9.2