Code: Brackets now become black when they are highlighted as "matching".
JSON: key names are now in "white" (json was a bit saturated with orange - keys and string values).
Cleanup: removed some unnecessary rules.
Default face color normalized to #ffffec (was #ffffe9).

Closes #2623

Using the CodeMirror-guttermarker and CodeMirror-guttermarker-subtle CSS
classes to give the markers their color.

Issue #2602

Closes #2415

Doesn't take up any space now, so that a tab of width 2 is 2 em width
rather than 3.

Added missing semicolon

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

Rather than adding a new rule.

Issue #1747

Closes #1744

This is the only theme that sets font size, remove this to bring in line
with other themes.

The double semicolon prevents LESS to compile the CSS file.

With the eclipse theme, if you move your cursor on a bracket and have the matching bracket option enabled, spans with borders are inserted. They push the rest of the line to the right by the amount of the border width, which looks very crappy. Using outline instead of border fixes this