* Update makefile to use dep
* Migrate to dep
* Fix some deps
* Try to find a better version for golang.org/x/net
* Try to find a better version for golang.org/x/oauth2
* Add support for extra sendmail arguments
* Sendmail args to exec.command should be a list
* Add go-shellquote package
* Use go-shellquote lib for parsing Sendmail args
* Only parse if sendmail is configured