Preserve whitespace at each block boundaries

[btk5h]

This should hopefully fix #713 and any of the duplicate issues people have filed.

This PR adds some logic that prevents whitespace from being trimmed at the end of each blocks.

[Conduitry]

Awesome! This one has been bugging us for a while, as you can see :)

About the test, though: Could you write this as a runtime test instead of as a js one? Runtime tests check for specific compiled behavior, rather than checking for specific code, and so are much less brittle.

[btk5h]

Is there an easy way to make runtime tests that are sensitive to whitespace differences?

The standard htmlEqual checks seem to ignore whitespace.

[Conduitry]

You're right, sorry, the normalizeHtml function is more aggressive than I thought, and would defeat a test for this. I suppose you could do an assertion on the raw string and compare target.innerHTML against some regular expression, and not use assert.htmlEqual at all. It's ugly, but I think it's still better than testing for specific compiler output.