Gather file descriptors as process metric

[paulbellamy]

Fixes #729

Any other bits we should to gather? I'm not super-convinced it's actually all that useful?

@2opremio, wdyt?

See "Open Files" sparkline below.

[2opremio]

I think it's a very useful metric, but I am not convinced it should have
such protagonism, or whether it's useful to show in a
sparkline.

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[tomwilkie]

Yes it would be good to have this hidden behind a show more.

On Friday, 12 February 2016, Alfonso Acosta notifications@github.com
wrote:

I think it's a very useful metric, but I am not convinced it should have
such protagonism, or whether it's useful to show it it's history in a
sparkline.

On Friday, February 12, 2016, Paul Bellamy <notifications@github.com
javascript:_e(%7B%7D,'cvml','notifications@github.com');> wrote:

Assigned #961 #961 to
@2opremio
https://github.com/2opremio.

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[paulbellamy]

Hiding a single element seems stupid.

Edit: However, I agree that it is less important. Thoughts, @davkal, @foot ?

[davkal]

@paulbellamy From my own debugging experience, open files gets you straight into root cause analysis, whereas cpu and memory are quite vague. so I love its prominence there (until a better metric comes along).

[davkal]

Tried the branch, JS part looks good too.

[2opremio]

minor-comments aside, LGTM