message: Replace the selected range instead of force-setting it
  This gives people the option of cutting parts or all of their message.
diff: @@ -209,9 +209,8 @@ export default class BasicMessageEditor extends React.Component {
  const selectedParts = range.parts.map(p => p.serialize());
  event.clipboardData.setData("application/x-riot-composer", JSON.stringify(selectedParts));
  if (type === "cut") {
  - // Remove the text from the composer
  - const {caret} = getCaretOffsetAndText(this._editorRef, selection);
  - this.props.model.update("", event.inputType, caret);
  + // Remove the text, updating the model as appropriate
  + replaceRangeAndMoveCaret(range, []);
  }
  event.preventDefault();
  }
  