Compatibility with steam-nodejs sentry file format

(Sorry about that - let me try the pull request again.)

I am migrating from node-steam-trash-bot to SteamBot.
After authenticating with my bot account, there was a 7-day enforced delay on trade due to Steam Guard.
I figured I would just copy the steam sentry file from my node-steam-trash-bot installation, but it failed.

SteamBot (and Steam itself) hashes the contents of the sentry file. node-steam-trash-bot just saves the hash to the file.This change is to support both file formats.