#273 Formatting lines as Todo removes hyperlink

[Matt K]

When formatting a list of items with todo checkboxes, the list loses any hyperlink formatting to other notes. This does not happen when formatting to ordered/unordered lists. I've added two screenshots of before and after.

To reproduce:

1) Select several lines of text that have hyperlinks to other notes
2) Hit the "todo" box on the toolbar to add checkboxes