Downloads Graph missing data

[Turbo87]

Migrated from #216:

/cc @alexcrichton

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One issue I see is that the "other downloads" section of the graphs isn't updated when you navigate between crates, for example if you click on the winapi crate and then on the libc crate you see this graph:

but if you reload the page you see:

[Turbo87]

hmm... I've tried to reproduce this problem, but it doesn't seem to happen consistently. It worked as expected for me most of the time and I've only seen it happen once. Not sure yet what might be causing this or how to reliably trigger it.