Merging LED example content

Using the original firmware already in repo to simplify stuff!
Merge pull request #2 from kennethlimcp/patch-1

Merging LED example content
Merge pull request #3 from kennethlimcp/master

upload ex-led.png(led_blink) and Read_button example
tweaks to make firmware compile
led_blink README tweaks
add note about LED polarity
toggle_led_with_api is looking good