Test that KeysFile does not begin with blank line

Author: Chris Hunt

spec/unit/github/auth/keys_file_spec.rb

@@ -49,6 +49,12 @@
         end
       end
 
+      it 'does not include a blank before the first key' do
+        subject.write! keys
+
+        expect(keys_file.read).to_not start_with("\n")
+      end
+
       it 'includes a newline after the last key' do
         subject.write! keys