Readme on copying a Node is out of date

[TimG1964]

The text on the Readme page currently says:

- Node is an immutable type. However, you can easily create a copy with one or more field values changed by using the Node(::Node; kw...) constructor where kw are the fields you want to change. For example:

node = XML.Element("tag", XML.Text("child"))

simple_value(node)
# "child"

node2 = Node(node, children=XML.Text("changed"))

simple_value(node2)
# "changed"

This seems to be a bit out of date. The Node() function seems to treat arguments as new children and keywords as new/changed attributes. The example presented now seems to create an attribute called "children" rather than changing the child node.

[joshday]

Just updated the example. Thanks for the issue!