Feature/test suite foundation

This pull request takes care of setting up the environment needed to add a test suite to OpenCobolIDE:

The test suite depends on tox and pytest:
```
pip install tox pytest
```

To run the tests for all supported Python versions:

```
tox
```

If you want to test only a specific Python version (e.g. Python 2.7), it's as easy as
```
tox -e py27
``` 

Tests are also run automatically on [Travis CI](https://travis-ci.org/OpenCobolIDE/OpenCobolIDE)

The initial test suite will contain:
  - a deployment test ```setup.py install``` 
  - an integration test that open a file, compile it and run the compiled program 

A more complete test suite will be introduced when working on the free-parser feature (#13)