Force gem version based on Ruby version in Travis

- Rack < 2.0 for Ruby < 2.2.2
- Json < 2.0 for Ruby < 2.0

Author: schneems

.travis.yml

@@ -8,6 +8,7 @@ rvm:
   - 2.0.0
   - 2.1
   - 2.2
+  - 2.3.1
 
 matrix:
   include:

Gemfile

@@ -1,2 +1,10 @@
 source "https://rubygems.org"
 gemspec
+
+if Gem::Version.new(RUBY_VERSION) < Gem::Version.new("2.2.2")
+  gem 'rack', '< 2.0'
+end
+
+if Gem::Version.new(RUBY_VERSION) < Gem::Version.new("2.0")
+  gem 'json', '< 2.0'
+end

gemfiles/Gemfile-1.9

@@ -1,3 +1,5 @@
 source "https://rubygems.org"
 gemspec path: '..'
 gem 'sass', '< 3.4'
+gem 'rack', '< 2.0'
+gem 'json', '< 2.0'