update edition guide for Rust 1.34

Fixes #203

src/SUMMARY.md

@@ -96,4 +96,6 @@
     - [`literal` macro matcher](rust-next/literal-macro-matcher.md)
     - [`?` operator in macros](rust-next/qustion-mark-operator-in-macros.md)
     - [const fn](rust-next/const-fn.md)
-    - [Pinning](rust-next/pin.md)
+    - [Pinning](rust-next/pin.md)
+    - [Alternative Cargo Registries](rust-next/alternative-cargo-registries.md)
+    - [TryFrom and TryInto](rust-next/tryfrom-and-tryinto.md)

src/rust-next/alternative-cargo-registries.md

@@ -0,0 +1,26 @@
+# Alternative Cargo registries
+
+Initially added: ![Minimum Rust version: 1.34](https://img.shields.io/badge/Minimum%20Rust%20Version-1.34-brightgreen.svg)
+
+For various reasons, you may not want to publish code to crates.io, but you
+may want to share it with others. For example, maybe your company writes Rust
+code that's not open source, but you'd still like to use these internal
+packages.
+
+Cargo supports alternative registries by settings in `.cargo/config`:
+
+```toml
+[registries]
+my-registry = { index = "https://my-intranet:7878/git/index" }
+```
+
+When you want to depend on a package from another registry, you add that
+in to your `Cargo.toml`:
+
+```toml
+[dependencies]
+other-crate = { version = "1.0", registry = "my-registry" }
+```
+
+To learn more, check out the [registries section of the Cargo
+book](https://doc.rust-lang.org/nightly/cargo/reference/registries.html).

src/rust-next/tryfrom-and-tryinto.md

@@ -0,0 +1,23 @@
+# TryFrom and TryInto
+
+Initially added: ![Minimum Rust version: 1.34](https://img.shields.io/badge/Minimum%20Rust%20Version-1.34-brightgreen.svg)
+
+The [`TryFrom`](../../std/convert/trait.TryFrom.html) and
+[`TryInto`](../../std/convert/trait.TryInto.html) traits are like the
+[`From`](../../std/convert/trait.From.html) and
+[`Into`](../../std/convert/trait.Into.html) traits, except that they return a
+result, meaning that they may fail.
+
+For example, the `from_be_bytes` and related methods on integer types take
+arrays, but data is often read in via slices. Converting between slices and
+arrays is tedious to do manually. With the new traits, it can be done inline
+with `.try_into()`:
+
+```rust
+use std::convert::TryInto;
+# fn main() -> Result<(), Box<dyn std::error::Error>> {
+# let slice = &[1, 2, 3, 4][..];
+let num = u32::from_be_bytes(slice.try_into()?);
+# Ok(())
+# }
+```