Add greasewatch, it displays nonempty cron files

~ arash@farm-machine
$ ./bin/greasewatch
data-pipeline-crunch (abtesting-pipelines-crunch):
    0 * * * * spotify-analytics-data greaserun --runner luigi etc. etc.
    0 * * * * spotify-analytics-data greaserun --runner luigi etc. etc.

data-pipeline-crunch (crunch-hashtags):
    0 * * * * spotify-analytics-data greaserun --runner luigi etc. etc.