Start main python script
Create a frame with a menu bar.

The software will have several buttons, but the idea of the menu
bar is to have redundancy on the commands and to inform the user
of the shortcuts.
Tie a matplotlib canvas to the frame

At this point is not doing anything special.
Add a button to open image.

The button opens a file dialog. By selecting a file and pressing OK,
the program does nothing at this stage.
Merge pull request #2 from leouieda/GUI

Initial GUI code