Vendor dependencies

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vendor/rand/README.md

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+rand
+====
+
+A Rust library for random number generators and other randomness functionality.
+
+[![Build Status](https://travis-ci.org/rust-lang-nursery/rand.svg?branch=master)](https://travis-ci.org/rust-lang-nursery/rand)
+[![Build status](https://ci.appveyor.com/api/projects/status/rm5c9o33k3jhchbw?svg=true)](https://ci.appveyor.com/project/alexcrichton/rand)
+
+[Documentation](https://docs.rs/rand)
+
+## Usage
+
+Add this to your `Cargo.toml`:
+
+```toml
+[dependencies]
+rand = "0.4"
+```
+
+and this to your crate root:
+
+```rust
+extern crate rand;
+```
+
+### Versions
+
+Version `0.4`was released in December 2017. It contains almost no breaking
+changes since the `0.3` series, but nevertheless contains some significant
+new code, including a new "external" entropy source (`JitterRng`) and `no_std`
+support.
+
+Version `0.5` is in development and contains significant performance
+improvements for the ISAAC random number generators.
+
+## Examples
+
+There is built-in support for a random number generator (RNG) associated with each thread stored in thread-local storage. This RNG can be accessed via thread_rng, or used implicitly via random. This RNG is normally randomly seeded from an operating-system source of randomness, e.g. /dev/urandom on Unix systems, and will automatically reseed itself from this source after generating 32 KiB of random data.
+
+```rust
+let tuple = rand::random::<(f64, char)>();
+println!("{:?}", tuple)
+```
+
+```rust
+use rand::Rng;
+
+let mut rng = rand::thread_rng();
+if rng.gen() { // random bool
+    println!("i32: {}, u32: {}", rng.gen::<i32>(), rng.gen::<u32>())
+}
+```
+
+It is also possible to use other RNG types, which have a similar interface. The following uses the "ChaCha" algorithm instead of the default.
+
+```rust
+use rand::{Rng, ChaChaRng};
+
+let mut rng = rand::ChaChaRng::new_unseeded();
+println!("i32: {}, u32: {}", rng.gen::<i32>(), rng.gen::<u32>())
+```
+
+## Features
+
+By default, `rand` is built with all stable features available. The following
+optional features are available:
+
+-   `i128_support` enables support for generating `u128` and `i128` values
+-   `nightly` enables all unstable features (`i128_support`)
+-   `std` enabled by default; by setting "default-features = false" `no_std`
+    mode is activated; this removes features depending on `std` functionality:
+    
+        -   `OsRng` is entirely unavailable
+        -   `JitterRng` code is still present, but a nanosecond timer must be
+            provided via `JitterRng::new_with_timer`
+        -   Since no external entropy is available, it is not possible to create
+            generators with fresh seeds (user must provide entropy)
+        -   `thread_rng`, `weak_rng` and `random` are all disabled
+        -   exponential, normal and gamma type distributions are unavailable
+            since `exp` and `log` functions are not provided in `core`
+        -   any code requiring `Vec` or `Box`
+-   `alloc` can be used instead of `std` to provide `Vec` and `Box`
+
+## Testing
+
+Unfortunately, `cargo test` does not test everything. The following tests are
+recommended:
+
+```
+# Basic tests for rand and sub-crates
+cargo test --all
+
+# Test no_std support (build only since nearly all tests require std)
+cargo build --all --no-default-features
+
+# Test 128-bit support (requires nightly)
+cargo test --all --features nightly
+
+# Benchmarks (requires nightly)
+cargo bench
+# or just to test the benchmark code:
+cargo test --benches
+```
+
+# `derive(Rand)`
+
+You can derive the `Rand` trait for your custom type via the `#[derive(Rand)]`
+directive. To use this first add this to your Cargo.toml:
+
+```toml
+rand = "0.4"
+rand_derive = "0.3"
+```
+
+Next in your crate:
+
+```rust
+extern crate rand;
+#[macro_use]
+extern crate rand_derive;
+
+#[derive(Rand, Debug)]
+struct MyStruct {
+    a: i32,
+    b: u32,
+}
+
+fn main() {
+    println!("{:?}", rand::random::<MyStruct>());
+}
+```
+
+
+# License
+
+`rand` is primarily distributed under the terms of both the MIT
+license and the Apache License (Version 2.0).
+
+See LICENSE-APACHE, and LICENSE-MIT for details.