Fix file permissions for .netrc fixture

Permissions must be 0600 or test will fail. Set using File.chmod in before block.

spec/octokit/client_spec.rb

@@ -86,6 +86,10 @@
       end
 
       describe "with .netrc" do
+        before do
+          File.chmod(0600, File.join(fixture_path, '.netrc'))
+        end
+
         it "can read .netrc files" do
           Octokit.reset!
           client = Octokit::Client.new(:netrc => true, :netrc_file => File.join(fixture_path, '.netrc'))