Add \n to gemfile end

This changes gemfile output as below:
index 702c934..70b3f1a 100644
--- a/gemfiles/rails4_0.gemfile
+++ b/gemfiles/rails4_0.gemfile
@@ -2,7 +2,8 @@

 source "https://rubygems.org"

 gem "actionpack", "~> 4.0.0.beta"
 gem "activesupport", "~> 4.0.0.beta"

-gemspec :path=>"../"
\ No newline at end of file
+gemspec :path=>"../"