Use better_errors for better errors

These two gems make it much easier to debug problems on the development machine.
Merge pull request #150 from KenYN/patch-1

Use better_errors for better errors
#141 change delayed_job.handler to mediumtext (16MB) like event.payload

This isn't a complete fix because if the event.payload is (say) exactly
16MB then the handler will be >16MB and the same problem will occur.

I'll push this in for now though, in practice it means it's much less
likely to occur.
add better_errors to Gemfile.lock
remove rails_admin_histories table from schema file
peak detector text shouldn't say "tweets"
Merge pull request #153 from albertsun/cleanup

Cleanup
Merge pull request #152 from Alex-Ikanow/update_handler_text_size

#141 change delayed_job.handler to mediumtext (16MB) like event.payload