Ignore the spaces separating a URL for a possible title.

Fixes https://github.com/pw374/omd/issues/38
Re-indent the body of `maybe_link`.
Remove trailing white space in URLs.

This is done whether or not a title follows the URL.  The reason is
that unescaped spaces are not allowed in URLs and it is likely that a
trailing white space is a mistake from the author (say, left after
removing a title).
Merge pull request #41 from Chris00/master

Remove trailing white space in URLs