Remove children from node terminals

The grammar doesn't specify that children count
as node terminator, but the text does.

The following document would be valid per text,
but invalid per spec.

```kdl
node { child {} }
```

Fixes #274

SPEC.md

@@ -63,6 +63,10 @@ slash-escaped line continuation](#line-continuation). Arguments and Properties
 may be interspersed in any order, much like is common with positional
 arguments vs options in command line tools.
 
+[Children](#children-block) can be placed after the name and the optional
+Arguments and Properties, possibly separated by either whitespace or a
+slash-escaped line continuation.
+
 Arguments are ordered relative to each other (but not relative to Properties)
 and that order must be preserved in order to maintain the semantics.
 
@@ -74,9 +78,8 @@ Nodes _MAY_ be prefixed with `/-` to "comment out" the entire node, including
 its properties, arguments, and children, and make it act as plain whitespace,
 even if it spreads across multiple lines.
 
-Finally, a node is terminated by either a [Newline](#newline), a [Children
-Block](#children-block), a semicolon (`;`) or the end of the file/stream (an
-`EOF`).
+Finally, a node is terminated by either a [Newline](#newline), a semicolon (`;`)
+or the end of the file/stream (an `EOF`).
 
 #### Example
 
@@ -182,7 +185,7 @@ my-node 1 2 3 "a" "b" "c"
 ### Children Block
 
 A children block is a block of [Nodes](#node), surrounded by `{` and `}`. They
-are an optional terminator for nodes, and create a hierarchy of KDL nodes.
+are an optional part of nodes, and create a hierarchy of KDL nodes.
 
 Regular node termination rules apply, which means multiple nodes can be
 included in a single-line children block, as long as they're all terminated by