`blink` example doesn't exist

[Qingwei Lan]

The line make flash-hail EXAMPLE=blink # Flash the example 'blink' program to the hail platform doesn't work because the the examples folder doesn't contain blink

$ make flash-microbit_v2 EXAMPLE=blink
LIBTOCK_PLATFORM=microbit_v2 cargo run --example blink  \
                --target=thumbv7em-none-eabi --release -- --deploy=tockloader
error: no example target named `blink`
make: *** [flash-microbit_v2] Error 101

$ make flash-microbit_v2 EXAMPLE=leds works though

[Johnathan Van Why]

README.md still needs to be updated after libtock-rs was substantially rewritten.

[Hudson Ayers]

Closing as a duplicate of #398