Bug fixes, views and helper refactorings, better specs and more test cases

I should have done more granular commits... I'll do that for the next pull requests :)

So to sum up the changes : 

1.  Included some conditions for when the entry creator visits entries. I added different logic conditions in the `like_status_for` helper to render a better phrase (tell me if you think it needs a different logic and feel free to change the phrases).
2.  Added the `like_status_for` helper to `users/show` view.
3.  Rephrased and moved specs from `spec/features` to `spec/helpers`. This fixes some horrible bugs in the specs which started giving me a bad headache...
4.  I modified the `like_button_for` helper to check whether the current_user is the entry creator. In this case the button isn't rendered. I can leverage on this modification for the future views refactoring (home/index, entries/index, users/show).
5.  I added specs for the `like_button_for` helper.