Replace dependency on webmozart/json

[geekish]

Currently using webmozart/key-value-store and webmozart/json to manage reads/writes to crap.json.

We are currently locked to an older version of composer/composer because webmozart/json requires a much older version of justinrainbow/json-schema (see webmozart/json#37).

So we need to either fork webmozart/json and provide our own JsonFileStore class, or come up with a new solution altogether. This could be a good time to make some changes as mentioned in geekish/crap#9.

[geekish]

Running into issues using crap now, since I can't update composer. I have unfortunately had to uninstall it for now, until I decide how to move forward.

I don't have much time to dedicate to PHP projects at the moment so if anyone uses this and would like to help I'll take it. :)