Extract list of differences

[RomainDeg]

As of now, the tool only returns a boolean result: whether the two input models are equal or not.
We want the tool to be able to return a list of differences between the two models (if such differences exists between two input models).

[AntoninGoslin]

A first version of this feature have been merged in PR #46.
Thanks to this version, we are able to extract a list of differences between two models.
Famix-Simple-Diff always returns a boolean indicating if the two models are the same or not, but we can also retrieve the list of differences stored in a dedicated instance variable (named differences).
For the moment we have 5 types of différences:

• an entity addition.
• an entity deletion .
• an entity that changed (rename for exemple).
• a relation that changed.
• a property that changed.

Each differences found created an object from the class FamixSimpleDifference.
Such an object contains 3 informations.

• the entity that changed.
• the expected value.
• the actual value.

This first version will probably need to be updated using Moose's meta models as seen in issue #4