immunize awk to absence of newlines

Appending 'RS=,' to awkcantation fixes aheissenberger's test case:
curl -A "Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; Trident/6.0)" -s 'https://api.github.com/repos/steeve/boot2docker/releases' | awk -F\" '/tag_name/{print $4;exit}' RS=,

yields:
v0.5.3

This works because it replaces awk's default Record Separator (RS) of '\n' with JSON's comma. Tested on same 3 random platforms as before.