Syntax highlighting with double-backslashes in regexes

The line

```
str.replace(/\\/g, '')
```

is perfectly valid CoffeeScript, removing all backslashes from a string. However, the regex `/\\/` doesn't get highlighted. Worse, if there's a slash later on the line, _then_ regex highlighting goes all the way up to it, e.g.

```
str.replace(/\\/g, '\\\\').replace(/\\"/g, '"')
```

highlights

```
/\\/g, '\\\\').replace(/
```

In short, the syntax highlighter isn't currently distinguishing between a single backslash (which escapes the closing `/` of a regex) and a double backslash (which doesn't). More precisely, it needs to ignore any _even_ number of backslashes preceding the closing `\`, since the current behavior is correct for a regex like

```
/\\\/foo/
```

No file or test is named. Locate the CoffeeScript TextMate syntax grammar and inspect its regex-matching rules; use the examples in the issue to verify that even backslashes do not close a regex while an odd number does. Done means both highlighted examples stop at the correct closing slash.

Written by the indexing model from the issue text.