Upgrade minimum reqiured version of Rust to 1.29

This upgrades the minimum required version of Rust to 1.29 in order to
fix BurntSushi#916 (Zombie processes cause `rg --files` to hang in `/proc`).

See also:
- Rust compiler bug ticket: rust-lang/rust#50619
- Rust compiler PR with the fix: rust-lang/rust#50630

closes BurntSushi#916

.travis.yml

@@ -62,13 +62,13 @@ matrix:
     # Minimum Rust supported channel. We enable these to make sure ripgrep
     # continues to work on the advertised minimum Rust version.
     - os: linux
-      rust: 1.28.0
+      rust: 1.29.0
       env: TARGET=x86_64-unknown-linux-gnu
     - os: linux
-      rust: 1.28.0
+      rust: 1.29.0
       env: TARGET=x86_64-unknown-linux-musl
     - os: linux
-      rust: 1.28.0
+      rust: 1.29.0
       env: TARGET=arm-unknown-linux-gnueabihf GCC_VERSION=4.8
       addons:
         apt:

README.md

@@ -337,7 +337,7 @@ If you're a **NetBSD** user, then you can install ripgrep from
 
 If you're a **Rust programmer**, ripgrep can be installed with `cargo`.
 
-* Note that the minimum supported version of Rust for ripgrep is **1.28.0**,
+* Note that the minimum supported version of Rust for ripgrep is **1.29.0**,
   although ripgrep may work with older versions.
 * Note that the binary may be bigger than expected because it contains debug
   symbols. This is intentional. To remove debug symbols and therefore reduce
@@ -358,7 +358,7 @@ ripgrep isn't currently in any other package repositories.
 
 ripgrep is written in Rust, so you'll need to grab a
 [Rust installation](https://www.rust-lang.org/) in order to compile it.
-ripgrep compiles with Rust 1.28.0 (stable) or newer. In general, ripgrep tracks
+ripgrep compiles with Rust 1.29.0 (stable) or newer. In general, ripgrep tracks
 the latest stable release of the Rust compiler.
 
 To build ripgrep: