use single quotes for values that contain double quotes

[OverFlow636]

This will use single quotes for attributes instead of double quotes, when the value contains double quotes.

Fix for cheeriojs/cheerio#720

[OverFlow636]

@fb55 any chance you can take a look at this? Thanks!

[crystalline]

+1 had the same problem with .. style = 'font-family: "Geneva";'> ... being serialized to style = "font-family: "Geneva";">
OverFlow636's patch fixed the problem

[briantjacobs]

This also fixed my problem on a page that had JSON within an html element within single quotes:

<div data-platform-social-links='[{"socialLink":{"icon":"icongs-facebook","class":"addthis_button_facebook","analyticsEvent":"Facebook"}}]'></div>

[Matthalp-zz]

This patch looks legitimate and addresses an important issue for parsing many Websites (e.g. msn.com and many others in the Alexa Top 100). Is there a reason the merge is being held off?