Minor stylesheet changes to padding/margin

Previously, if you collapsed the “Frame Data” panel, a three pixels high
gap would show. This commit fixes that by removing the 3px bottom
padding from ‘.openingpanel’s. This lead to the bottom of the content
inside the panels being to close to the bottom of the panels, so the
-3px margin was removed as well.

Also, the spacing of the ‘moreinfo’ list entries (the links to the
comic, explainxkcd, et.c) has been changed from “10px above each entry”
to “5px vertically around each entry” to fix the same problem. The
spacing between the entries remains the same, but now there is a larger
gap between the last entry and the end of the “More Info” panel.
Fix bug where panels couldn’t be closed

Sometimes, the init function for a panel throws an exception. (For me,
this happens during local testing because my setup isn’t complete.)
Since that function is called from the slideToggle callback, the
exception would be thrown to jQuery, which apparently didn’t like that,
with the effect of subsequent slideToggles no longer working. Fix by
catching (and ignoring) any exceptions in the callback.
Center logo below “at your own pace” h2

This centers the AYOP logo horizontally in regard to the width of the
“at your own pace” h2 element.

The IE≤9 warning was moved because between the h2 and the logo, it would
have caused _these_ to be centered in regards to the warning’s width,
which completely breaks all kinds of design on the page. The element
will still mess up the page, but not quite as bad.
Fix link in IE≤9 warning

‘-’ → ‘=’
Minor grammar/spelling fixes

* “back wards” → “backwards”
* “github” → “GitHub”
Move the logo down by 10 pixels

…without moving all elements that come after the logo.
Fix plurality: "Pause special frames: X second(s)"

Depending on whether the input is 1 or not, the text changes from
"seconds" to "second" and back.
Fix dark theme canvas glow
Remove the PLI left border from dark theme

was dashed, but looked very weird with dark’s round corners
Fix debated frame glow bug

Frames after a debated frame would keep their "debated" glow because of
a misinterpretation of the isDebated() function by
updateAllWithoutSliders(). isDebated() only checks the debated ratio and
must always be used in conjunction with isSpecial().

Added an explanatory comment to isSpecial().
Merge pull request #145 from lucaswerkmeister/master

Minor changes, fixes and additions