Use a saner log line format
Add more debugging output
Clean up method naming
Output a message when being killed
Make code more readable and idiomatic:

 - Make variable names clearer
 - Use debug logging
 - Use more idiomatic Ruby looping
 - Make log messages clearer
Log errors at error log level
Add support for multiple logging levels
Default the log level to info
Make variable naming more succinct but still meaningful
Remove extraneous variables
Attempt to make code clearer:

 - Simplify variable names
 - Make setting pull request status less cluttered
 - Add logging
 - Simplify conditionals
Make logging of pull request status changes more centralised
Simplify logic
Simplify variable names. Log build status changes.
Log if there are no PRs that require testing.
Add a handler for SIGINT
Make method name simpler
Split conditional across multiple lines, for readability
Handle setting up log level in bin script, to make code more testable
Get tests passing