README.md: Add samd51, accelerometer crate, micromath crate

- Adds a link to `samd51` in addition to `samd21`, and updates the
  project's location
- Adds a new "Component abstraction crates" section and lists the
  `accelerometer` crate
- Adds the `micromath` crate to the "no-std crates" section

Author: tarcieri

README.md

@@ -117,7 +117,8 @@ Peripheral Access Crates were also called Device Crates.
 
 ### Microchip
 
-- [`atsamd21`](https://github.com/wez/atsamd21-rs) Peripheral access API for Microchip (formerly Atmel) SAMD21 microcontrollers.  This git repo hosts both the peripheral access crate and the hal.
+- [`atsamd21`](https://github.com/atsamd-rs/atsamd) Peripheral access API for Microchip (formerly Atmel) SAMD21 microcontrollers.  This git repo hosts both the peripheral access crate and the hal.
+- [`atsamd51`](https://github.com/atsamd-rs/atsamd) Peripheral access API for Microchip (formerly Atmel) SAMD51 microcontrollers.  This git repo hosts both the peripheral access crate and the hal.
 - [`sam3x8e`](https://crates.io/crates/sam3x8e) Peripheral access API for Atmel SAMD3X8E microcontrollers (generated using svd2rust)  - ![crates.io](https://img.shields.io/crates/v/sam3x8e.svg)
 
 ### Nordic
@@ -317,6 +318,13 @@ Crates tailored for specific boards.
 
 - [`betafpv-f3`](https://github.com/JoshMcguigan/betafpv-f3) - For the BetaFPV F3 drone flight controller
 
+## Component abstraction crates
+
+The following crates provide HAL-like abstractions for subcomponents of embedded
+devices which go beyond what is available in [`embedded-hal`]:
+
+- [`accelerometer`](https://github.com/NeoBirth/accelerometer.rs) - Generic accelerometer support, including traits and types for taking readings from 2 or 3-axis accelerometers and tracking device orientations - ![crates.io](https://img.shields.io/crates/v/accelerometer.svg)
+
 ## Driver crates
 
 Platform agnostic crates to interface external components. These crates use the [`embedded-hal`]
@@ -577,6 +585,7 @@ Work in progress drivers. Help the authors make these crates awesome!
 - [intrusive-collections](https://crates.io/crates/intrusive-collections): intrusive (non-allocating) singly/doubly linked lists and red-black trees - ![crates.io](https://img.shields.io/crates/v/intrusive-collections.svg)
 - [managed](https://crates.io/crates/managed): provides `ManagedSlice`, `ManagedMap` backed by either their std counterparts or fixed-size buffers for `#![no_std]`. - ![crates.io](https://img.shields.io/crates/v/managed.svg)
 - [menu]: A basic command-line interface library. Has nested menus and basic help functionality. ![crates.io](https://img.shields.io/crates/v/menu.svg)
+- [micromath](https://github.com/NeoBirth/micromath): Embedded Rust math library featuring fast, safe floating point approximations for common arithmetic operations, 2D and 3D vector types, and statistical analysis - ![crates.io](https://img.shields.io/crates/v/micromath.svg)
 - [nalgebra](https://crates.io/crates/nalgebra): general-purpose and low-dimensional linear algebra library - ![crates.io](https://img.shields.io/crates/v/nalgebra.svg)
 - [nom](https://crates.io/crates/nom): parser combinator framework - ![crates.io](https://img.shields.io/crates/v/nom.svg)
 - [num-format](https://crates.io/crates/num-format): Crate for producing string representations of numbers, formatted according to international standards, e.g. "1,000,000" for US English - ![crates.io](https://img.shields.io/crates/v/num-format.svg)