Add a big green download button.

[hvenev]

Fixes #2113, #1592, #1219, #65.

Note that the node ember proxy is a bit broken on Firefox. The browser sends Accept: text/html, and ember interprets it as a request to not proxy to crates.io. No such problem was observed with Chromium.

I've not tried to make this pretty either in terms of UI or in terms of code. It is just a demonstration of an approach to solve the issue.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @jtgeibel (or someone else) soon.

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[Turbo87]

thanks for the PR @hvenev!

#1592 (comment) explains our reasons for why we don't want to have a "Download" button on the crate pages though. I hope you understand. :)

[bronson]

Maybe, instead of a big green button, you could add a link to that issue?

I just spent 20 minutes trying to figure out how to download crates. 5 minutes of that was clicking all over thinking "there's GOT to be a download button on here somewhere and I'm too blind to find it."