Add line number ranges

[seankim658]

For potentially very large files, add an argument that allows you to specify a range to render for.

Initial thoughts is it will follow Python slicing convention. For example, 60, 70 will render only lines 60 to 70, 60, _ will render from line 60 to the end of the file, _, 60 will render from the beginning of the file to line 60.

Only potential issue is that this will be applied globally across all included files so the user will have to be aware of that.