Doesn't recognize italics which end with a single quote

[ShawnTheBeachy]

For example, the string "*Italic'*s" will be parsed as:

String: *
String: Italic'
String: *
String: s

Instead of:

Emphasis: Italic'
String: s

[Knagis]

This is according to the specification. http://spec.commonmark.org/dingus/?text=*Italic%27*s

If you believe that this is not correct, the issue should be raised at the CommonMark repository.