Kyutae Lee

So that it does not record NaN. Now gif is always generated after an evaluation. For the case you do not want this pull request, I divided this pr from...

Enable saving replay

7

Enhancement suggestion from [@e6p77Bi8CW7zRBg](https://twitter.com/e6p77Bi8CW7zRBg): It would be good if a user can save replay.

Enable restarting

1

Enhancement suggestion from [@e6p77Bi8CW7zRBg](https://twitter.com/e6p77Bi8CW7zRBg): It would be good if we can restart the game when both peers agree.

Before this fix, `tsub_ok(-1, INT_MIN)` returned `0`, which is not a correct result since the subtraction `(-1) - INT_MIN` does not cause overflow. (The result of the subtraction `(-1) -...

This pull request fixes some typos in the text.

I think the feature of #27 (which is reverted by #28) should be re-merged after its completeness is improved. The feature is now tracked on [webrtc-additional-setting](https://github.com/gorisanson/pikachu-volleyball-p2p-online/tree/webrtc-additional-setting) branch.