Add serialization of the test data to json

[JulianWgs]

closes #28

It has been a long time :D but I got around to implement an initial support for exporting serialized results.

This is a draft to get feedback in as soon as possible.

To do:

• Export word list as well
• Do exports on key press when viewing the results screen
• Export results after every test with a config option
• Set export location via GUI and config
• Have unique filenames (using timestamps)
• Add option to add additional metadata about test (such has keyboard used)

Considering the resulting format I would propose to stick as close to original data structures as possible and export all available data. In my opinion this export is for experts, who want to their own analysis in a programming language.

[lain-ok]

I'm anticipating the merge on this PR, results history would provide some fascinating insight on hand. My typing speed as actually gone up considerably using this project (from around 50wpm - 80wpm on the default language).

I have also has the idea of using the acg/w3m project to pipe articles summaries into ttyper to enhance memory retention of core concepts and ideas.

[JulianWgs]

With this code I already exported a lot of test data and analyzed them with Python. I could gain a lot of interesting insights about my typing, which was very useful, because I bought a new keyboard.

• Where should I put this analysis code?
• Should I complete the rest of the task as written above or do you want to propose some changes?