auto merge of #15162 : steveklabnik/rust/install_instructions, r=brson

This has my voice *very strongly*. I'm not sure if it's too much. I'd find it okay if I had to tone it back, and I don't want it to be _too strong_, but clinical docs are boring.

src/doc/guide.md

@@ -7,4 +7,103 @@ displayed here in line with Rust's open development policy. Please open any
 issues you find as usual.
 </div>
 
-Coming soon. :)
+## Welcome!
+
+Hey there! Welcome to the Rust guide. This is the place to be if you'd like to
+learn how to program in Rust. Rust is a systems programming language with a
+focus on "high-level, bare-metal programming": the lowest level control a
+programming language can give you, but with zero-cost, higher level
+abstractions, because people aren't computers. We really think Rust is
+something special, and we hope you do too.
+
+To show you how to get going with Rust, we're going to write the traditional
+"Hello, World!" program. Next, we'll introduce you to a tool that's useful for
+writing real-world Rust programs and libraries: "Cargo." Then, we'll show off
+Rust's features by writing a little program together.
+
+Sound good? Let's go!
+
+## Installing Rust
+
+The first step to using Rust is to install it! There are a number of ways to
+install Rust, but the easiest is to use the the `rustup` script. If you're on
+Linux or a Mac, All you need to do is this:
+
+```{ignore}
+$ curl -s http://www.rust-lang.org/rustup.sh | sudo sh
+```
+
+(If you're concerned about `curl | sudo sh`, please keep reading. Disclaimer
+below.)
+
+If you're on Windows, please [download this .exe and run
+it](http://static.rust-lang.org/dist/rust-nightly-install.exe).
+
+If you decide you don't want Rust anymore, we'll be a bit sad, but that's okay.
+Not every programming language is great for everyone. Just pass an argument to
+the script:
+
+```{ignore}
+$ curl -s http://www.rust-lang.org/rustup.sh | sudo sh -s -- --uninstall
+```
+
+If you used the Windows installer, just re-run the `.exe` and it will give you
+an uninstall option.
+
+You can re-run this script any time you want to update Rust. Which, at this
+point, is often. Rust is still pre-1.0, and so people assume that you're using
+a very recent Rust. 
+
+This brings me to one other point: some people, and somewhat rightfully so, get
+very upset when we tell you to `curl | sudo sh`. And they should be! Basically,
+when you do this, you are trusting that the good people who maintain Rust
+aren't going to hack your computer and do bad things. That's a good instinct!
+If you're one of those people, please check out the documentation on [building
+Rust from Source](https://github.com/rust-lang/rust#building-from-source), or
+[the official binary downloads](http://www.rust-lang.org/install.html). And we
+promise that this method will not be the way to install Rust forever: it's just
+the easiest way to keep people updated while Rust is in its alpha state.
+
+Oh, we should also mention the officially supported platforms:
+
+* Windows (7, 8, Server 2008 R2), x86 only
+* Linux (2.6.18 or later, various distributions), x86 and x86-64
+* OSX 10.7 (Lion) or greater, x86 and x86-64
+
+We extensively test Rust on these platforms, and a few others, too, like
+Android. But these are the ones most likely to work, as they have the most
+testing.
+
+Finally, a comment about Windows. Rust considers Windows to be a first-class
+platform upon release, but if we're honest, the Windows experience isn't as
+integrated as the Linux/OS X experience is. We're working on it! If anything
+does not work, it is a bug. Please let us know if that happens. Each and every
+commit is tested against Windows just like any other platform.
+
+If you've got Rust installed, you can open up a shell, and type this:
+
+```{ignore}
+$ rustc --version
+```
+
+You should see some output that looks something like this:
+
+```{ignore}
+rustc 0.11.0-pre (443a1cd 2014-06-08 14:56:52 -0700)
+host: x86_64-unknown-linux-gnu
+```
+
+If you did, Rust has been installed successfully! Congrats!
+
+If not, there are a number of places where you can get help. The easiest is
+IRC, which you can access
+[here](http://chat.mibbit.com/?server=irc.mozilla.org&channel=%23rust). Click
+that link, and you'll be chatting with other Rustaceans (a silly nickname we
+call ourselves), and we can help you out. Other great resources include our
+[mailing list](https://mail.mozilla.org/listinfo/rust-dev),
+[subreddit](http://www.reddit.com/r/rust), and
+[StackOverflow](http://stackoverflow.com/questions/tagged/rust).
+
+## Hello, world!
+
+## Hello, Cargo!