extract scope from whole line

[gregsadetsky]

When extracting scope of current selection, check if boundary chars (first and last) are single or double quotes. if so, use this file name. This works for situations such as:

<link href="app.css" rel="stylesheet">

when the cursor is placed anywhere in the app.css text.

Otherwise (if bounding chars are not single or double quotes), extract the current selection's line, and check for src=['"].+['"] and failing that, href=['"].+['"]. This will work with the above <link> with the cursor placed anywhere.