Fix a bad array reference when there are no acronyms.

If we just use `$this->acronyms` we don't have an array that is imploded, so our line parsing next won't work.
Replace the Acronym followed by anything that is not another word character.

This gets acronyms ending in a period to work. Fixes #1.
Trim up the text we'll use as the title attribute.

For some reason I was getting line breaks.