Multi-line links inside lists confuse syntax highlighting.

[alercah]

Links that span multiple lines inside lists confuse the highlighting:

1. [foo
     bar](baz)

In this case, "foo bar" should get the link highlight. Instead, "foo" gets the link highlight, "bar" does not, and then the rest of the document (!) gets highlighted as links.

[tpope]

Removing markdownLineStart from the contains on markdownLinkText seems to fix it. Can you try that for a week and report back as to whether that causes any problems?

[tpope]

And if there aren't any issues, a pull request would be great.