Adjust full-width captions to clear properly; Adjust sidenote and marginnote margin when occuring inside blockquotes

[ghost]

Fixes #23 and #24

Here is a test page for the fixes: http://fullwidthtest.surge.sh/test/

• The caption clears properly while the width of the caption is maintained across screen size transitions.
• Sidenotes and Marginnotes have correct margins when occurring inside blockquotes

The first change is at L235 however my editor apparently removed a lot of trailing whitespaces, thus the high number of altered lines in that specific diff