fixParamsAndReturns = function(doc) {
  if (doc.params) {
    _.each(doc.params, function(param) {
      replaceNewLines(param, 'description');
    });
  }

  // Replace new lines in the return and params descriptions.
  var returns = doc.returns;
  if (returns) {
    replaceNewLines(returns, 'description');
  }
}
Remove the duplicate param annotations. Go through the params and the return
annotations to replace the new lines and escape the types to prepare them
for markdown rendering.

@param {!Object} doc Document representing a function jsdoc.