FIX: Avoid matching tag names that contain the current tag name.

The .\{-} match for the remainder is too lax; it can pick up intermediate tags where the current tag name is a subset of, e.g. the GSP <g:else> and <g:elseif> tags.
If there's content after the tag name, it must be separated by whitespace.
Also, as no attributes are allowed on the end tag, the pattern can be restricted to only optional whitespace.
Merge pull request #17 from inkarkat/fix-avoid-tag-subset-matches

FIX: Avoid matching tag names that contain the current tag name.