Showing file menu, but still not doing anything
Main window with menu file option_ Loading working
fixed bugs in __main__ of manipulator
removed NotImplementedError + added example in __main__ as naive test
added simple history functionality to the Manipulator
added key bindings to go back and forth in simple history + bug fix
Merge branch 'master' of https://github.com/dporro/spaghetti
Merge branch 'master' of https://github.com/dporro/spaghetti