History tools

[ronkot]

Relates to #4.

This PR has the following functionality:

• Writes used routes to $HOME/.routahe_history
• Updates usage count and timestamps per route
• Offers api to query history data:
  • history.add(from, to): Add / update route
  • history.get(): Get whole history
  • history.latestRoute(): Get latest route
  • history.topRoute(): Get most used route

Routes are of type

{
    from: 'Address 1',
    to: 'Address 2',
    count: 1,
    timestamp: 100
}

This PR does not yet offer command line api to history data, as the api is going to change in near future.

Feel free to comment!

[ronkot]

Updated PR to use file $HOME/.routahe and data structure

{
  history: []
}

...which allows easy future expansions. If new properties are added to data structure, it's probably best to move the basic file handling functions to a separate file for common use.