Update rspec-rails to 3.4.2

The changes in rspec-rails 3.4.1 to fix the problems with Rails 4.2.5.1
introduced a performance regression due to template lookup not being
cached. Timing tests show that it doesn't really affect our controller
specs (probably due to the large amounts of factories created) but it's
a minimal change so worth having.

Gemfile.lock

@@ -242,15 +242,15 @@ GEM
       rspec-core (~> 3.4.0)
       rspec-expectations (~> 3.4.0)
       rspec-mocks (~> 3.4.0)
-    rspec-core (3.4.1)
+    rspec-core (3.4.2)
       rspec-support (~> 3.4.0)
     rspec-expectations (3.4.0)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.4.0)
     rspec-mocks (3.4.1)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.4.0)
-    rspec-rails (3.4.1)
+    rspec-rails (3.4.2)
       actionpack (>= 3.0, < 4.3)
       activesupport (>= 3.0, < 4.3)
       railties (>= 3.0, < 4.3)