Update config.js

Allow configuration of mail by advice-type.
Update mailer.js

only send mail of the type declared in the config.mail.what array.
fixed exchange checker
Update btce.js
Gekko can't pull GHS balance from cex.io

issue 63
Merge pull request #84 from Devouring/master

Gekko can't pull GHS balance from cex.io
abstracted out exchange config checker
Merge pull request #62 from ItsLeeOwen/config-mail

Config email by type of advice
merge latest from main
added config and log folders, log folder and config/user folder both ignore all files, just a nice trick to have the default folder structure setup for scripts and such