[sass mode] Remove hard-coded lists of html tags and pseudo-elements

Issue #1466
[sass mode] Remove unused variable
Updated sql's hookIdentifier to properly match escaped `
Preserve Doc.prototype.constructor property
Preserve constructor property on the editor instance.

In some cases it's more convenient to access `CodeMirror`
from the instance itself, but the way prototype was defined
made it impossible.
[markdown mode] Directly use xml mode, rather than relying on text/html binding

Since the mode uses the internals of the xml mode state object, it
will break if another mode defines text/html (i.e. htmlmixed).

Closes #1468
[css mode] Add @import context
[sql mode] Don't consider '.e' a number

Closes #1489
Give the line wrapper a CSS class CodeMirror-code

Issue #1492
[css mode] Properly make keywords case-insensitive

Also prevent Object.prototype properties like toString from
being interpreted as keywords.

Closes #1495
add gutter filler
Add coverGutterNextToScrollbar option

Issue #1493
Fix copy/paste in IE
Simplify 53bc4b1f54670c827662d5210a37b35e63a07c39
add overwrite mode ("R") to vim keymap
Document toggleOverwrite method
[lint addon] Don't use -span- in css classes

Apparently Bootstrap messes with those.

Closes #1497
vim mode: Add tests covering word selection behavior.
vim mode: Fix off-by-one errors in word selection.

The below conforms to Vim's behavior regarding whitespace trimming.
Add CodeMirror Eclipse to real-world uses