Make LoadFromString not panic but return an error instead.

Change-Id: I9f52fe807c8e9771a530f90ede8bd46fcdb467ae
Delete MustLoadFromString, as nobody needs it.

Change-Id: Ib95c316857ffdd36d973c0e8701967de99d78b13
Update the vendoring of bmizerany/perks/quantile.

This is still from my own fork as there are still critical PRs that
bmizerany hasn't responded to yet.

Change-Id: Ib46e68ec9ecbae9423b1bfe1311569426dfc7ba0
Make extraction honor ms-precision timestamps.

The test touched by this commit exposed the bug already.

Change-Id: I303131eab841ae0ea9b1a727230e68754a4cd8fe
Add a few trailing commas to tests.

That is to prove that trailing commas work for the processor.

Change-Id: Ibecac811d47958387c9633df69bafbe284cf0b8f
Merge pull request #35 from prometheus/u-c-l/maintenance

Just a couple of minor things maintenance.
Add procfs package with support for fds
Add basic standard exports
Add goroutines exporter
Add procfs support for /proc/[pid]/stat
Export cpu, memory and start time standard metrics
Cleanup procfs
Update exports