Remove an unnecessary trailing line break before end tag.

[takahisa]

refs: #44

When parsing markdown text as follows, it contains an unexpected trailing line break in the output. I add a procedure that removes this unnecessary line break from the parsing result.

source markdown text:

* item1
* item2

1. item1
2. item2

foo bar
baz

output:

<ul><li>item1
</li><li>item2
</li></ul><ol><li>item1
</li><li>item2
</li></ol><p>Lorem ipsum dolor sit amet, consectetur adipisicing elit,
sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
</p>

output (apply this patch)

<ul><li>item1</li><li>item2</li></ul><ol><li>item1</li><li>item2</li></ol><p>Lorem ipsum dolor sit amet, consectetur adipisicing elit,
sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.</p>