Add rust implementation

[Romira915]

• Add Rust implementation.
• Only docker-compose

[catatsuy]

It is difficult for me to maintain the Rust implementation. Sorry. But I would suggest the following.

• You publish your Rust implementation in your repository and I will link to it from the README of this repository.
• Let me know when you are ready. I will post the link.

And I have something to tell you. Actually, Ruby implementation is the original implementation and Go implementation is ported from Ruby implementation. Some parts of the implementation are changed for Go's convenience.

private-isu/webapp/ruby/app.rb

Line 80 in 9d21a60

`printf "%s" #{Shellwords.shellescape(src)} | openssl dgst -sha512 | sed 's/^.*= //'`.strip

private-isu/webapp/golang/app.go

Line 124 in 9d21a60

out, err := exec.Command("/bin/bash", "-c", `printf "%s" `+escapeshellarg(src)+` | openssl dgst -sha512 | sed 's/^.*= //'`).Output()

Probably, you should use duct::sh instead of duct::cmd. Thanks. @Romira915

[Romira915]

Thank you for the suggestion. Suggestion accepted and fixed.
And it's ready to go. Here is my repository.

[catatsuy]

@Romira915 I think you should have a repository for only Rust applications such as the following repository.

https://github.com/methane/pixiv-isucon2016-python

Because it is difficult for people who actually want to use your code to use it if it is forked.

[Romira915]

I Understood. Accordingly I have created a rust only repository.

https://github.com/Romira915/private-isu-rust

Thank you. @catatsuy

[catatsuy]

Thank you. I added your repository on README. @Romira915