Implement error bars using standard deviation on timeline plots

[str4d]

Recreated from #113 on current master.

[str4d]

Two things:

• This is going to cause merge conflicts with Add support for displaying median benchmarks #203, so once that is ready and merged I can rework this PR.
• Once Add support for displaying median benchmarks #203 is merged this should be extended to only show the error bar toggle for mean benchmarks.

[tobami]

Reviewing #203 ...

One thought occurred to me: before trying to re-add a complex feature like error bars, do you think it makes sense to reevaluate now what plotting library we use? jqPlot has been unmaintained for over two years now. flot is pretty similar and still widely used, if a bit simpler (may not have all the features). There are also other alternatives. Any thoughts here?

[str4d]

I don't personally have an opinion. I've never used any JavaScript plotting libraries prior to setting codespeed up; since then I have now used jqPlot and d3, but only just enough to get the features I wanted working 😜

[tobami]

Ah, it seemed like you had experience with plotting libraries! Let's leave that question for now then.

[tobami]

@str4d are you going to rebase this branch onto master?

[str4d]

Sorry for the delay, work's been keeping me busy. I'll do this Friday 😄

[tnorth]

I'm also interested in this change, therefore a kind ping @str4d :-)

[tnorth]

Ok, I merged it quickly, it works for me but since I don't know the internals of codespeed, I can't tell if I broke something.
The merge commits are here: https://github.com/tnorth/codespeed/commits/master

[tobami]

Nice, thanks @tnorth! I'll do some "visual" testing of it 😄

[str4d]

Sorry for dropping the ball on this! I'll be doing some more codespeed work in the next few weeks, so I'll get this integrated while I do :)

[str4d]

Rebased on 0.11.0 (because that's what I've been working from locally), and fortunately there are no merge conflicts with master!

[tobami]

Could you rebase on top of master just in case? I merged some big refactors affecting default branches.

[str4d]

Rebased on master, still appears to work for me!

[tobami]

I checked and the error bars are shown, well done! However, the padding has been increased.

Before:

After:

(this is with testdata.json)

[str4d]

That padding change appears to be left over from the original PR #113 (see e.g. #113 (comment)). I can try playing around with the contents, but not being the original author I don't immediately know the cause.