include relevant output in signal files, and send to healthchecks.io when available

• we currently function based solely on the presence of files in ok/warning/error directories, and do not read/write the contents of these files
• we should improve our healthchecks such that they output relevant details into these files
• we should improve our reporter such that the relevant details are shipped to healthchecks.io when available: https://healthchecks.io/docs/attaching_logs/