fix for gem dependency issue #175

Twitter gem `5.0.0` was recently released (18th Nov) and causes issues with our dependency on;  json, '~> 1.7.6'

:lock: - This PR locks the Twitter gem we use to `~> 4.8.1`.

:newspaper:  - Work will be underway soon to update all gem dependencies in lolcommits, and use (more up-to-date) specific versions set in lolcommits.gemspec.