Need good default error reporting settings

[tdmalone]

Need to ensure that all possible errors, warnings and notices that PHP reports are effectively set to go somewhere the administrator will see them.

• On Heroku, Papertrail works well for this, but we need to ensure the config is correct so every error goes there by default.
• On Docker, we need to ensure we're setting up the right settings and have somewhere to send the data. Maybe just to the error_log file will be fine? (although if not mounting the local file system over /var/www/html its possible it won't ever be seen)

Then we can also remove the ini_set()'s from init.php.

[tdmalone]

Heroku errors should be fixed now by https://github.com/tdmalone/slackemon/commit/9f428bbe36bb8ff71c7ff7770fb95fd95a3f9160#diff-e9fa0d13b445ed0246ee0003db4374d6 - ini_set was redirecting them, ha!