support for space in file name + percent in width/height

[ironbishop]

This code provides:

• (multiple) space(s) in file name
• percent dimensions (html5 compliant)

See regular expression tests before and after.

From this:
{% img [class names] /path/to/image [width] [height] [title text [alt text]] %}
To this:
{% img [class names] /path/to/image[ file].ext [width[%]] [height[%]] [title text [alt text]] %}