Closes #1992

HTML5 tag parsing hack, and invert css media query.

Closes #1984

Closes #1975

To prevent it from being visible on dark backgrounds.

when they do so, they don't indicate the start of a string.

The gutter element would end up before any 'above' widgets, causing
the widgets to hide it.

Closes #1971

Most modern browsers now keep displaying the placeholder even if the
user has focus on the input and only hide it when the input has content.

This change is to make this addon consistent with this, so users won't
tell the difference with native inputs' placeholder behaviour.

Issue #1972
Issue #1967

Issue #1969

Issue #1969

Issue #1908

Issue #649

Issue #649

Issue #1960

`cm-s-ambiance` and `CodeMirror-focused` are classes to the same
element, so search for `.cm-s-ambiance .CodeMirror-focused` will fail.

Issue #1947

It's possible to provide custom markup for hint elements that are LI
tags and that breaks event delegation logic that expects UL to have
text-only LI nodes. As a result if you have elements inside LI and
click/dblclick on those, nothing happens and selected hint is not
applied. The fix improves event delegation in the way to find nearest
parent element to event target that is a hint element at the same time.