Better events

- When removing a node, a `"changenext"` event only fires when the removed node previously had a next node;
- When removing a node, a `"changeprev"` event only fires when the removed node previously had a prev node;
- When inserting a node, a `"changenext"` event only fires when the inserted node now has a next node;
- When inserting a node, a `"changeprev"` event only fires when the inserted node now has a prev node;
- When setting a value of a Text node, a `"changetext"` event only fires when the value actually changed.
Fixed a styling issue where a line was 80 characters
0.0.10