Add build branch to version information

[otoolep]

Enhance the information displayed by the version command, to minimize any confusion about built code.

[otoolep]

Example output:

$ ./influxd version
InfluxDB v1.0 (git: master 1234)

[otoolep]

@toddboom

[corylanou]

I wonder if we should add that to the http headers as well, or maybe that's getting to noisy. Currently we send down the version header with each request, but not the build:

https://github.com/influxdb/influxdb/blob/master/services/httpd/handler.go#L674

Thoughts?

[otoolep]

@corylanou -- I think that would be too noisy. I think just the version is the right thing to do for HTTP headers, but I don't feel that strongly about it.

[corylanou]

I don't feel that strongly either. If they really need it, it will be in the log from when they start.

[beckettsean]

@otoolep @corylanou I could see adding the full information into the HTTP headers when hitting the /ping endpoint, otherwise it seems unnecessary. If it's not trivial to do it only for the ping endpoint then I say leave it out for now.

[otoolep]

@corylanou -- does this get a +1 from you?

[corylanou]

+1