Updated mail gem 2.6.1 -> 2.6.3
Updated sass-rails gem 4.0.3 -> 4.0.4 and sprockets 2.11.0 -> 2.11.3

The newer sprockets version fixes a minor vulnerability.
Updated aws-sdk 1.55.0 -> 1.57.0
Updated devise gem 3.4.0 -> 3.4.1
Updated devise_invitable gem 1.3.6 -> 1.4.0
Update feedjira gem 1.4.0 -> 1.5.0 and sax-machine gem 1.0.1 -> 1.0.2
Updated newrelic_rpm gem 3.9.5.251 -> 3.9.6.257
Updated puma gem 2.9.1 -> 2.9.2
Upgraded capybara-webkit gem 1.3.0 -> 1.3.1
Updated factory_girl gem 4.4.0 -> 4.5.0 and factory_girl_rails gem 4.4.1 -> 4.5.0
Updated launchy gem 2.4.2 -> 2.4.3
Updated sqlite3 gem 1.3.9 -> 1.3.10
Updated yard gem 0.8.7.4 -> 0.8.7.6
Update rspec-core 3.1.4 -> 3.1.7
Updated redis gem 3.0.7 -> 3.1.0 and redis-namespace gem 1.4.1 -> 1.5.1
Updated rspec-expectations 3.1.1 -> 3.1.2
Updated rspec-mocks gem 3.1.1 -> 3.1.3
Updated arbre gem 1.0.1 -> 1.0.2
Downgraded sidekiq gem 3.2.5 -> 3.2.4

Hey, don't look at me. It looks like versions 3.2.5 and 3.2.6 were yanked from rubygems or something. I can't find anything in the github bugtracker for sidekiq, but just in case I'm trusting bundler and allowing it to downgrade to 3.2.4 when I run a "bundle update sidekiq".
Experimental branch: get rid of the Feedjira gem.

Feedjira brings a dependency on curb. This is highly inconvenient because the gem is dragged into my project despite it not being used ever (I'm only using Feedjira's parsing capabilities, not its fetching capabilities), and most importantly, makes the whole app incompatible with JRuby (because curb is not supported in recent JRuby versions).

I'm gonna see what happens if I get rid of Feedjira (and that annoying curb dependency) and instead use the stdlib RSS module to parse feeds.