Add file location to misspellings

[jonaprieto]

Instead of:

Misspelled words:
<url-free> README.md: html>body>h1>a>img[alt]

Is it possible to get something more useful, such as:

Misspelled words:

./README.md:ROW:COLUMN:
html>body>h1>a>img[alt]

[facelessuser]

That context is often not available. For instance, the current markdown filter uses Python Markdown which does not track line numbers. HTML could maybe return line numbers depending on what HTML parser it is using, but I don't think line numbers are guaranteed to be available.