Keep the last sound alert in memory

[silomia]

With the new version 1.6, we can choose different sound alerts. However, when we open a new timer, the sound alert number one is selected by default. I would like Timer to keep my last choice for the next time.
In addition, for those who don't want any sound, this is also a good way (see request #19 ).

[karbassi]

Something to consider.

PRs welcome. Maybe @simongroenewolt, who implemented #107 ?

[robinstewart]

BTW @simongroenewolt if you're up for working on this, it's just a few lines of code — when the user changes the sound, you set that sound number to a key in UserDefaults; then when a new timer is created, you read it back out from UserDefaults instead of always choosing the first sound. (The UserDefaults framework does all the hard work of persisting to disk between sessions etc.)

[karbassi]

@robinstewart Submit a PR! :)