always sort list of files

sometimes listFiles can read feed2 before feed1
same problem was fixed in #42, but reverted in 0fc724d

```ruby
Loading data from path: /home/ruslan/work/falcon-regression/merlin/target/test-classes/hcat/hcat-process.xml (BundleUtil:102)
Loading data from path: /home/ruslan/work/falcon-regression/merlin/target/test-classes/hcat/feed-template2.xml (BundleUtil:102)
Loading data from path: /home/ruslan/work/falcon-regression/merlin/target/test-classes/hcat/cluster-0.1.xml (BundleUtil:102)
Loading data from path: /home/ruslan/work/falcon-regression/merlin/target/test-classes/hcat/feed-template1.xml (BundleUtil:102)
```