Updates to Gemfile

This does:

* use sf-te branches
* use micro_migrations from a regular gem (the gist sometimes crapped
  out)
* remove data_migrations (not used anyway)
* update safe_yaml, because 0.9.4 has been yanked meanwhile
* set jruby-openssl to require: false and require it manually in
  hub.rb, because this caused tons of warnings about existing constants
  when running rake
require jruby-openssl in bin/hub
make loading raven conditional
do not report memory usage if metrics reporting is turned off
do not overwrite GH setup
setup metrics
declare reporting exchange and builds.linux queue in hub
bundle update after rebase
bump travis-core
remove newrelic, add metriks-librato_metrics
use sudo: false
Merge pull request #29 from travis-ci/sf-te

Changes from sf-te