Display an error if a particular config line is malformed

[leonsodhi]

Currently, r_s2 won't complain if the following config is used:

files:
  /home/leon/test.log
destination:
  host: HOST.papertrailapp.com
  port: PORT
  protocol: tls

Output:

sudo ./remote_syslog -c ./example_config.yml -D
2014-10-09 18:38:13 INFO  remote_syslog.go:114 Connecting to HOST.papertrailapp.com:PORT over tls

No files are being monitored but it's not clear why that's the case.

[chmac]

I was just kicked in the teeth by this same error. We had protocol: UDP which I eventually realised from the strace logs is invalid. But I didn't get any error from remote_syslog itself. I'd suggest that remote_syslog fail to start if the config file is invalid, otherwise it's a real brain bender to track down.

[snorecone]

I'm closing this since invalid port strings such as "PORT" will cause remote_syslog to cease startup as of v0.19:

cannot parse 'Destination.Port' as int: strconv.ParseInt: parsing "PORT": invalid syntax

If there are other config options that should be validated in a special way, I'd open an issue for each specific option.