Clarify documentation in readme.md

[Firstyear]

Quickstart and readme's need to display how to use dfu-util to flash, IE don't say "dfu-util -D" actually list the path to the .dfu file dn all examples. Copy-paste is a good test :)

Readme in root should list toboot to perform the bootloader upgrade - better, include the prebuilt from toboot in this repo, and have instructions here to update them.

The macos prereqs should be brew tap osx-cross/arm && brew install arm-gcc-bin instead of the arm-gcc website.

[jeffre]

brew tap osx-cross/arm && brew install arm-gcc-bin

Thank you for that! The arm-gcc website has depreciated the url too.