Online-judge-verify-helper

- 236 support Nim (chaemon)
- 239 fix the bug that `oj-verify` crashes when there are files whose `include` directives are broken
- 238 add `.gitignore` to `.verify-helper/.gitignore`
- 237 add a workaround for a bug of installation of online-judge-tools

- 212 fix a bug of bundler about `include` with relative paths

- 200 detect available compilers and add settings to specify compilers and options
- 204 add `--config-file` option
- 207 fix a bug about timestamps (key-moon)
- 209 fix a bug about escaping (key-moon)

- 192 improve C++ bundler
- 193 194 improve document generator
- 196 improve logging

- 179 improve generated documents a little
- 183 188 add `verification_file_suffix` field to `config.toml`
- 185 improve stability
- 187 add a workaround about stack overflow on WSL

- 175 176 fix some bugs