better handling of rails version checks

lib/jasmine/headless/task.rb

@@ -42,7 +42,7 @@ module Jasmine
 
       private
       def create_rails_compliant_task
-        if Rails.version >= "3.1.0"
+        if Rails.respond_to?(:version) && Rails.version >= "3.1.0"
           desc 'Force generate static assets without an MD5 hash, all assets end with -test.<ext>'
           task 'assets:precompile:for_testing' => :environment do
             Rails.application.assets.digest_class = Digest::JasmineTest

spec/lib/jasmine/headless/task_spec.rb

@@ -21,6 +21,7 @@ describe Jasmine::Headless::Task do
     end
 
     context 'with Rails' do
+      context 'without version' do
         before do
           module Rails
             def self.version
@@ -33,6 +34,21 @@ describe Jasmine::Headless::Task do
           Jasmine::Headless::Task.new('jasmine:headless')
         end
       end
+
+      context 'with version' do
+        before do
+          module Rails
+            def self.version
+              return "0"
+            end
+          end
+        end
+
+        it 'should be OK if rails is defined' do
+          Jasmine::Headless::Task.new('jasmine:headless')
+        end
+      end
+    end
   end
 
   describe 'jasmine:headless integration test' do