Update README.md to remove smart magic quote

On some versions of Chef and Ruby (particularly those currently available on AWS Opsworks), the smart magic quote in the README.md can cause installation errors:

    /opt/aws/opsworks/local/lib/ruby/gems/2.0.0/gems/json-1.8.1/lib/json/common.rb:155:in `encode': "\xE2" on US-ASCII (Encoding::InvalidByteSequenceError)

This is an consequence of the following Chef bug, which has since been fixed: https://tickets.opscode.com/browse/COOK-522