Rails 4

[Task 229] (https://integracredit.acunote.com/projects/44826/tasks/229) - update moribus gem to support rails 4

### Changes
* Refactored code according to rails 4 requirements (mostly done by @zbelzer)
* Fixed tracked tracked behavior

### RSpec
```
Finished in 5.84 seconds
46 examples, 0 failures
```

### Docs
```
Files:          12
Modules:        16 (    0 undocumented)
Classes:         1 (    0 undocumented)
Constants:       3 (    0 undocumented)
Methods:        29 (    0 undocumented)
 100.00% documented
```