Require newline after Reference.
Require newline after Reference.

Fletcher Penney pointed out the following bug in the previous
version:

![][figure]

[figure]: fig.png "caption" width=75%

is correctly *NOT* interpreted as a reference by most implementations
due to the extraneous width attribute.  Peg-markdown, however, strips
the fig.png part, and leaves the "caption" and width as leftover text
in the following paragraph:

<p><img src="fig.png" alt="" /></p>

<p>&quot;caption&quot; width=75%</p>

sftrabbit/MarkdownParse,sftrabbit/MarkdownParse,sftrabbit/MarkdownParse