update nokogiri

[#68]
don't need jbuilder

[#68]
update newrelic_rpm

[#68]
don't need launchy or binding_of_caller (?)

[#68]
update rails_12factor

[#68]
update sass-rails

[#68]
update uglifier

[#68]
update bitters

[#68]
update bugsnag

[#68]
update better_errors

[#68]
update brakeman

[#68]
update capybara

[#68]