Vanish tag

[felipeochoa]

Especially with React 16, it would be nice to have a single command to unwrap the children of a tag and splice them into the surroundings:

let c = <Parent><Child/><Parent>; // point on Parent

after vanishing parent should give:

let c = <Child/>; // point right before Child

• [X] Initial implementation
• [ ] Clean up whitespace outside the removed tag (e.g., extra newlines)
• [ ] Clean up whitespace when first/last child are text nodes
• [ ] Fix indentation for children
• [ ] If only child is text, wrap it in quotes
• [ ] Set point and mark to the start/end of the child region (or reversed if point was on the closer)
• [ ] Add tests