Remove requirement for unique titles

[sarmentow]

Right now when you create a note with an already used title, an error pops up saying that there's already a note with the same title. I think this probably hurts the usability of the app especially when you're just trying to jot down something.

It's probably very simple to fix this. I'm thinking about adding an id field to the Note class, and indexing/identifying the notes through this id instead of relying on the title field.

I would like to try this out and send a pull request. There are some other tweaks that could be done to improve usability once this feature is done. The app could show not only the title but a small preview (maybe the first few words or line) of each note in the list. This way if you have 2 notes with the same title but different contents you can distinguish between them. I could also work on this, perhaps I'll put this in a different pull request.

I'm not sure if the project is inactive. If so, I'll just fork it and implement these features.