add GitHub Flavored Markdown to README
add GitHub Flavored Markdown to README

* This makes the example code easier to read,
  especially when perusing the docs on github

yamill/ios-picker,mobilejohnw/ios-picker,yamill/ios-picker,MobileXLabs/ios-picker,danielzev/ios-picker,Ink/ios-picker,MobileXLabs/ios-picker,danielzev/ios-picker,mobilejohnw/ios-picker