Fix Travis failure by specifying Capybara version

Capybara 2.1.0 requires 1.9.3+ so we install a version that works with every
Ruby version we test against. This can be removed if we stop testing against
1.9.2.

The non-development dependencies are unchanged.

.travis.yml

@@ -3,10 +3,6 @@ rvm:
   - 1.9.3
 before_install:
   - gem update --system
-    # Capybara 2.1.0 requires 1.9.3+ so we install a version that works with
-    # every Ruby version we test against. This can be removed if we stop testing
-    # against 1.9.2.
-  - gem install capybara -v '< 2.1.0'
 branches:
   only:
     - master

fake_braintree.gemspec

@@ -25,6 +25,10 @@ Gem::Specification.new do |s|
   s.add_dependency 'thin'
 
   s.add_development_dependency 'rspec', '~> 2.12.0'
+  # Capybara 2.1.0 requires 1.9.3+ so we install a version that works with
+  # every Ruby version we test against. This can be removed if we stop testing
+  # against 1.9.2.
+  s.add_development_dependency 'capybara', '~> 2.0.3'
   s.add_development_dependency 'bourne', '~> 1.3'
   s.add_development_dependency 'timecop', '~> 0.6'
   s.add_development_dependency 'rake'