allow saving machines to LocalStorage

[CSchank]

• Use Elm ports to save a dictionary of the machine and tape they're working on.
• Autosave the machine every so often
• Allow them to create multiple machines (and load them!).
• When they load one machine, save the current one automatically.
• Show a little "Saved just now" text at the bottom of the screen?
• Allow them to name the machines ("Untitled" by default, save it even if they don't know about saving).
• Always load the last machine they were working on when they visit (or the even/odd one if they've never visited)
• Show an icon of the machine?

Architecture:

• pass in all machines (and any other things, like the last version, see #46) at the beginning as a flag
• have a single port to save all machines, Elm will just pass the raw string and JavaScript will store it

[CSchank]

• [x] Use Elm ports to save a dictionary of the machine and tape they're working on. Saved to server instead
• [x] Autosave the machine every so often
• [x] Allow them to create multiple machines (and load them!).
• [x] When they load one machine, save the current one automatically.
• [x] Show a little "Saved just now" text at the bottom of the screen?
• [x] Allow them to name the machines ("Untitled" by default, save it even if they don't know about saving).
• [x] Always load the last machine they were working on when they visit (or the even/odd one if they've never visited)
• [ ] Show an icon of the machine? Not done yet