Update location of rubygems.org credentials

No longer using .gemrc, so tell them to update their .gem/credentials file instead!

Ref: #694
Merge pull request #695 from parkr/patch-1

Update location of rubygems.org credentials
Update capybara to version 2.4.1
Use latest rubygems client
Update i18n to version 0.6.11
Update librato-rails to version 0.11.1
Update tzinfo to version 0.3.40
Update newrelic_rpm to version 3.9.0.229
Update rest-client to version 1.7.1
Update fakeredis to version 0.5.0
Update redis to version 3.1.0
Update xml-simple to version 1.1.4
Update will_paginate to version 3.0.7
Update high_voltage to version 2.2.0
Update rails to version 3.2.19
Gem::Builder merged into Gem::Package in rubygems 2.0.0
Test against the latest Ruby 2.1 and ruby-head
Update fog to version 1.22.1
Update clearance to version 1.3.0
Update delayed_job_active_record to version 4.0.1