Cleaned up indentation / standardised comments

Was just working on a tweak to see if I could get the title on post.hbs to always be vertically centred whilst maintaining the existing scroll animations. Not quite there yet, but in the mean time I did spot that the HBS files seemed to be a mix of 2, 4 and 0 space indentation - so I moved them all to 4 spaces for readability (also same standard Ghost core uses). And I converted HTML comments to Handlebars comments for cleaner (and smaller) final sourcecode output.

Pedantic changes - but hopefully make everything a little more readable and a little faster.