bump ruby to 2.1.5
update gems

minitest 5.4.3
mini_portile 0.6.1
nokogiri 1.6.4.1
mail 2.6.3
sass 3.4.8
bootstrap-sass 3.3.1.0
bourbon 3.2.3
simplecov 0.9.1
dotenv-deployment 0.0.2
dotenv 0.11.1
launchy 2.4.3
foreman 0.75.0
gon 5.2.3
listen 2.8.0
guard 2.8.2
guard-rails 0.7.0
sexp_processor 4.4.4
js_stack 1.3.0
netguru_theme 0.2.1
newrelic_rpm 3.9.7.266
pry-rescue 1.4.1
rails-assets-select2 3.5.2
rails_layout 1.0.24
rollbar 1.2.9
require underscore 1.6.0

underscore 1.7.0 have some breaking changes and it is not compatible
with backbone/marionette
remove unused code