Fix whitespace handling for img tags

"<img> content" is beautified to become "<img>content".  However, the
space should be preserved, as it has meaning.  This commit fixes this
issue by being more careful to preserve whitespace in the appropriate
places.
Fix indentation
Merge remote-tracking branch 'jcharum/improve-whitespace-handling'

Conflicts:
	js/lib/beautify-html.js
	js/test/beautify-tests.js
Tweak provided code to pass tests after merge

Closes #403, #415
Fixes #454