use absolute path to scripts directory

[philbot9]

Hi there,
I noticed the scripts will not run if the server is started from a different directory (i.e. node /some/path/dockerhub-webhook/index.js). The problem is that the path to the scripts directory in lib/run-script.js is relative.

[coveralls]

Coverage remained the same at 97.297% when pulling 28238e7 on philbot9:absolute-script-path into b5cec1e on maccyber:master.

[maccyber]

Thanks!

[philbot9]

No problem. Good work btw, it's been churning away nicely on the server.