Clarify documentation points.

[Firstyear]

README.md doesn't include:

• What to do after dfu-util has completed in the prebuilt directory
• dfu-util usage with prebuilt should be in the first paragraph for "quickstart" instead of down the page
• Should contain what version the firmware "will be"
• Should contain instructions on how to verify the firmware successfully flashed (lsusb or system information on osx)

These would help make the "new user" experience better.