auto merge of #15211 : steveklabnik/rust/guide_skeleton, r=huonw

This diff will look better once bors takes care of #15183

@brson and I talked about it, and, if I commit this skeleton, I can submit PRs for each portion, without doing this silly "builds on previous PRs" stuff, and it shouldn't cause conflicts.

This lays out what I think the guide should cover, and in what order.  I haven't picked a cohesive project yet that shows all this off, but I think this progression of concepts is appropriate.

Author: bors

src/doc/guide.md

@@ -411,3 +411,64 @@ rest of your Rust career.
 
 Next, we'll learn more about Rust itself, by starting to write a more complicated
 program. We hope you want to do more with Rust than just print "Hello, world!"
+
+## If
+
+## Functions
+
+return
+
+comments
+
+## Testing
+
+attributes
+
+stability markers
+
+## Crates and Modules
+
+visibility
+
+## Compound Data Types
+
+Tuples
+
+Structs
+
+Enums
+
+## Match
+
+## Looping
+
+for
+
+while
+
+loop
+
+break/continue
+
+iterators
+
+## Lambdas
+
+## Generics
+
+## Traits
+
+## Operators and built-in Traits
+
+## Ownership and Lifetimes
+
+Move vs. Copy
+
+Allocation
+
+## Tasks
+
+## Macros
+
+## Unsafe
+